Here are a few questions about computers I’ve received recently from people like you, and my answers. I have edited and restated the questions a bit, for readability.

Recently, you reviewed some new Apple laptops whose batteries are sealed in and can’t be removed by the user. But I have had situations with some laptops where the only way to restart them when frozen is to remove the battery. How can this problem be handled if the battery is sealed in?

On Mac laptops, you can shut down the computer, even if the software appears frozen, by holding down the power button firmly and continuously for 5-10 seconds. You then wait a few seconds, press the power button again, and the machine should start up. This is different from the more common scenario where a brief press of the power button brings up a dialog box allowing you to choose to shut down or restart the Mac, or to put it into sleep mode.

Apple says there is another method you can use instead of removing a battery. Pressing the Control and Command keys simultaneously with the Power Button restarts the computer.

I live in the U.S. and when I visit Europe I have no cellphone, which makes it difficult to stay in touch during my trips. I am completely ignorant about cellphones and use a pay-as-you-go model that doesn’t work in Europe. What type of phone do you recommend I buy that I can use both in the States and abroad? I do not need a built-in camera, or any other fancy add-ons. I only want to be able to call people.

The two major U.S. phone carriers whose underlying technology is compatible with the system used in Europe are AT&T and T-Mobile. Given your needs and your usage pattern, I’d go into one of their stores and look for the least expensive and simplest model that can operate on all the frequencies used in the U.S. and Europe. These phones are typically referred to as “quad band” or sometimes as “world phones.” I would also try and find a plan that minimizes overseas roaming charges, which can be quite high.

Another option is to look for an “unlocked” phone that can accept different SIM cards, the small chips that connect phones to carriers. That way, you could have one SIM for use in the U.S. and another for whatever country you are visiting.

I have hundreds of folders in “My documents.” In each folder there may be hundreds more individual files. Is there a way to rapidly search for key words in all of those documents in order to locate any files that might contain a particular word?

If you are using Windows XP, you can download and install various desktop search add-on products that can solve your problem. The best known are Windows search, from Microsoft, at http://bit.ly/Dflai, and Google Desktop Search, at desktop.google.com. If you have Windows Vista, it comes with a built-in desktop search function that can accomplish that task, though you can also use the Google product.

You can find Mossberg’s Mailbox, and my other columns, online for free at the All Things Digital web site, http://walt.allthingsd.com.

I have a USB cell phone data card that I use with my laptop. This card offers me world-wide connectivity wherever there is GSM cellphone service available. Is there an adapter that will allow me to use this card with the iPod Touch?

I know of no such adapter, nor of the software that would be needed to make one work. However, although the iPod Touch has no cellphone capability, it does include Wi-Fi, which can give you high-speed Internet access world-wide whenever you are in range of a Wi-Fi wireless network.

What U.S. cellphone service provider should I consider when purchasing a new contract and phone that can be easily used in most western European countries and also get good coverage in the U.S.?

In the United States, the only two major carriers that use the technology compatible with European networks are AT&T and T-Mobile. As to which has better coverage in the U.S., my own anecdotal experience is that this varies greatly depending on where you are, and that neither has coverage that’s as good as Verizon’s in as many major cities. However, Verizon (like Sprint) uses a technology that isn’t compatible with European networks, though it has one or two phone models that include both technologies.

I have just switched to the Mac from Windows. Is there a tutorial somewhere on how to use the Mac user interface and operating system?

There are a couple of books on switching to the Mac, which you can find at online bookstores. Also, Apple maintains two free, illustrated online tutorials called “Mac 101″ and “Switch 101,” the latter being specifically for former Windows users. They are available at apple.com/support/mac101 and apple.com/support/switch101.

You can find Mossberg’s Mailbox, and my other columns, online free at the All Things Digital Web site, http://walt.allthingsd.com.

This week, I was swamped with questions about Apple’s hot new iPhone, so this is a special all-iPhone edition of Mossberg’s Mailbox.

Can you physically remove the included AT&T SIM card from the iPhone and replace it with another AT&T card or one from another wireless carrier?

Yes, and no. The SIM card, which carries the iPhone’s account information, can be removed by inserting a paper clip into a tiny hole at the top of the phone. However, Apple says that if you replace the included card with one from another carrier, like T-Mobile in the U.S., or Orange in Europe, the phone won’t work. According to Apple, some non-iPhone AT&T cards may work, but some may not.

It’s possible that hackers will figure out a way to override this lock on other carriers’ SIM cards. But, as of now, the iPhone will work only with AT&T. Even overseas, at least until Apple does deals with foreign partners, you won’t be able to use SIM cards from other carriers. The iPhone will work overseas, but you will have to roam with AT&T and pay high charges. For instance, according to an AT&T spokesman, if you make a call in Europe, it would cost $1.29 a minute. It would cost 99 cents a minute if you are on one of AT&T’s $5.99 per month international plans.

Since the iPhone battery is sealed in and can’t be easily replaced by the user, what happens when it dies? Will you have to buy a new iPhone?

No, but you will have to send the phone to Apple, or drop it off at an Apple store, to have the battery replaced. The battery is covered during the phone’s one-year warranty period. After that, replacing the battery costs $79, plus $6.95 for shipping, and takes three business days. Details are at apple.com/support/iphone/service/battery/. Some small companies may eventually offer to do this for less, or in less time, as they have for the iPod.

One twist: because a phone is a necessity, Apple is offering loaner iPhones for $29 while your phone’s battery is being replaced, or for the period of any other repair on the iPhone. You will have to switch the AT&T SIM card from your own phone to the loaner, and then back again. Details are at apple.com/support/iphone/service/faq.

In addition, Apple warns that all the data on your iPhone will be wiped out during a battery replacement, but notes that it can easily be restored by simply syncing again with the iTunes software on your computer once you get it back with a fresh battery. That’s because, whenever you sync your iPhone with iTunes, it backs up the data on the phone. You can also use this method to fill your loaner iPhone with your own data.

Can I use the iPhone via a Bluetooth wireless connection in my car? Can I use Bluetooth to transfer files or other information between the iPhone and a computer?

In my two-week test of the iPhone, I succeeded in connecting it without much trouble to the built-in audio system and microphone on a friend’s BMW. Almost instantly, the over 700 contacts I had on my test iPhone were displayed on the car’s dashboard screen and calls could be made and received through the iPhone.

However, this first iPhone can use Bluetooth to connect only with cars and with wireless phone headsets. It cannot use Bluetooth to transfer any data to or from a computer, to play music through stereo wireless headsets, or for any other purpose. As with many other missing features, Apple has the ability to add these to the iPhone through software updates delivered by synchronizing with your computer.

If the iPhone’s Web browser is so good, why can’t it play video on Web sites I visit?

At launch, the iPhone version of the Safari browser is missing some plug-ins needed for playing common types of Web videos. The most important of these is the plug-in for Adobe’s Flash technology. Apple says it plans to add that plug-in through an early software update, which I am guessing will occur within the next couple of months. However, a separate program included on the iPhone can play a limited selection of videos from YouTube, and the phone can play videos you purchase from Apple’s iTunes store, and certain videos you create yourself.

You have been critical in the past of some smartphones that don’t allow you to delete emails with a single click. Can the iPhone do this?

Yes. If you are reading an email and want to delete it, you just tap on a trash can icon at the bottom of the screen and the message disappears into the trash can with an animation that resembles water being poured through a funnel.

However, in the iPhone email program’s list view, it takes two steps to delete an email. You have to swipe across the message header or preview with your finger, and then tap the red delete button that appears. You can also press an “Edit” button, which allows you to delete emails in the list view, but this still requires two taps per message.

Unlike on a BlackBerry or Treo, the iPhone doesn’t allow you to delete whole groups of email en masse by date, or even to select large groups and then delete them en masse. This would be a good feature for Apple to add down the line.

Can you buy an iPhone and just use it to play music and videos like an iPod, and to surf the Web or get email over Wi-Fi, without signing up for an AT&T service contract?

No. None of the iPhone’s functions, except calling 911, will work unless the phone is covered by a two-year AT&T service contract, and has been “activated” by AT&T. That will cost you $60 a month at a minimum. If you are thinking of buying an iPhone, you should plan on being an AT&T customer, and if AT&T coverage is poor where you live, work and travel frequently, I advise you NOT to buy an iPhone.

You and many others have criticized AT&T’s EDGE data network, which the iPhone uses, as slow. You have noted that AT&T has a much faster data network. Can the iPhone be upgraded to use that faster network?

No, it can’t. This first edition of the iPhone can’t use any cellular network faster than EDGE, which is much, much slower than the fastest cellphone data networks available from AT&T, Verizon or Sprint. It can, however, use very fast Wi-Fi wireless networks, when you are in range of them.

Apple hasn’t said anything about future iPhone models, but I fully expect a future model that can use these faster cellular networks, which are usually called 3G networks. So, if this is very important to you, I’d suggest waiting to see if such an iPhone emerges. But I don’t expect this to happen anytime soon.

In the past few days, AT&T seems to have tweaked its EDGE network, at least in some locations, so it runs faster than it has in the past. In my own speed tests, around Washington, D.C., I have seen repeated speeds of around 150 kilobits per second, roughly 50% better than the 100 kbps I have seen with EDGE in the past. However, I have also recorded speeds as slow as 82 kbps. And, even the new, faster speeds are way below those of the faster American cellular data networks, which can easily reach 500 to 800 kbps on a phone.

How good is the iPhone’s To-Do list or Task function?

Awful — in the sense that it doesn’t exist. The phone does have a calendar, of course, which syncs with the most popular calendar programs on Windows and Macintosh computers. And it has a Notepad, which doesn’t sync with any program on any computer (though you can email notes to yourself and others). But it has no To-Do list function at all.

Write to Walter S. Mossberg at mossberg@wsj.com

Here are a few questions about computers I’ve received recently from people like you, and my answers. I have edited and restated the questions a bit, for readability. This week my mailbox contained questions about accessing financial sites on a nonsecure Internet connection, which cellphones with email capability to take abroad, and what to do about Web sites that don’t work well in Safari.

I am concerned about security on my laptop when traveling and using nonsecure Internet connections available at motels. Is there a way to be secure when accessing my financial Web sites while using a motel’s connection?

You can install a good firewall, and sweep your laptop with security software for spyware and other malicious software that might transmit passwords. And you can make sure you are using antiphishing software. Better yet, you could use a sort of private Internet tunnel, called a Virtual Private Network, or a remote control service, like GoToMyPC, so you are actually using your home PC — remotely — to contact the Web sites involved.

But, the bottom line is that, unless you are on a network that you can control and secure, such as a home or office network, I wouldn’t advise accessing financial accounts online, or performing financial transactions. I wouldn’t trust sensitive online transactions to any public Internet connection, such as those at motels. There are too many people, including other guests, the motel staff, and the people at the company that provides the motel’s Internet service, who could potentially be watching what you are doing.

Is there a cellular phone that can be taken abroad that has a good email capability, for a comfortable price?

That depends on what you’d consider “good” email capability, or what price would be “comfortable” for you. It also depends on what countries you’re heading for. But, in general, any BlackBerry or Treo that works with the AT&T (formerly Cingular) or T-Mobile networks here in the U.S. will work in Europe and in many other regions. And both have what I consider good email capabilities for the price, which can vary, depending on model, and be as low as $99.

In general we love our new MacBook laptop, but there is one thing we’re not sure how to work around. We find that there are some Web sites that don’t seem to work well with the built-in Safari browser, and on some sites, we are unable to play a video. Is there a solution?

Yes. For the Web pages that don’t work well with Safari, you can download and use as an alternative the Firefox browser, which comes in a Mac version that is essentially identical to its Windows version. You can get Firefox, which is free, at mozilla.com.

The videos that won’t play were likely produced in the latest version of Microsoft’s Windows Media format. Microsoft offers free software that allows these videos to play on a Mac. It’s called Flip4Mac and can be downloaded at: www.microsoft.com/windows/windowsmedia/player/wmcomponents.mspx.

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Because of the volume of email I receive, I can’t routinely answer individual questions by email, or consult on individual problems or purchasing decisions. I read all questions I receive and select three each week to answer in the column.

Write to Walter S. Mossberg at mossberg@wsj.com

Here are a few questions about computers I’ve received recently from people like you, and my answers. I have edited and restated the questions a bit, for readability. This week my mailbox contained questions about the “Links” toolbar in IE 7.0, smartphones with Wi-Fi chips and information on high-definition TVs.

I know you are a big fan of tabbed browsing, but I really liked having my most frequently visited Web sites on the “Links” toolbar at the top of the browser in the previous version of Internet Explorer. Is this feature totally absent in the new IE 7.0?

Tabbed browsing and the Links bar aren’t mutually incompatible, and in fact I heavily employ both in every Web browser I use, including IE 7.0, Firefox and Safari (the Links bar is called the Bookmarks Toolbar in Firefox and the Bookmarks Bar in Safari).

To turn on the Links toolbar in IE 7.0, click on the Tools icon at the upper right, highlight “Toolbars” from the drop-down menu, and click on “Links” in the list that appears. That entry should now be designated with a check mark and the Links toolbar should appear, just as it did in the previous version.

Here’s another IE 7.0 tip. If you want to see IE’s familiar menus, which are turned off by default in the new version, click on that same Tools icon at the upper right and then click on “Menu Bar” from the drop-down menu.

Are there any smartphones like the Treo that have built-in Wi-Fi chips? I’d like to be able to use the phone’s Web browser at a Wi-Fi hot spot without using minutes. I imagine the cellphone carriers aren’t eager to offer this dual capability.

Yes, there are a few smartphones that have both the ability to access the cellphone network and the ability to use Wi-Fi wireless data networks — even though, as you note, the cellphone-network operators generally shun the idea. The latest of these is the T-Mobile Dash, which I reviewed a few weeks back. For my review, go to: ptech.wsj.com/archive/ptech-20061130.html. T-Mobile is a bit different from the other American cellphone carriers because it alone has a significant business in running commercial Wi-Fi hot spots.

Hewlett-Packard also makes a PDA that has both cellphone and Wi-Fi capabilities. It’s called the iPAQ Mobile Messenger hw6925 and is also sold by Cingular Wireless, though only to “business customers.” The new Nokia E62, sold in the U.S., doesn’t include Wi-Fi, but its nearly identical European counterpart, the E61, does, and it can be used in the U.S. by just popping in a chip, called a SIM card, from a U.S. carrier like Cingular or T-Mobile.

I’m thinking about getting a high-definition plasma or LCD television. Needless to say, I found your review helpful, but would like further information. Is there a Web site or sites you could recommend?

The Web site CNET has an excellent HDTV buyer’s guide, packed with lots of information and good explanations. It’s at: hdtv.cnet.com.

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Because of the volume of e-mail I receive, I can’t routinely answer individual questions by e-mail, or consult on individual problems or purchasing decisions. I read all questions I receive and select three each week to answer in the column.

Write to Walter S. Mossberg at mossberg@wsj.com

Here are a few questions about computers I’ve received recently from people like you, and my answers. I have edited and restated the questions a bit, for readability. This week my mailbox contained questions about Cingular data networks, the quality of Compaq laptops and options for connecting an iPod to home speakers.

In your review of the new T-Mobile BlackBerry Pearl, you said Cingular Wireless has a data network that is much faster than the EDGE network that T-Mobile uses. But I have a BlackBerry from Cingular and it, too, uses EDGE. So how is Cingular faster?

In 80 cities, Cingular has now rolled out a new network based on a technology called HSDPA that, in my tests, can be 10 times as fast as EDGE. However, most of its phones and digital devices haven’t been updated in new versions that can use the new, faster network. So far, only a few regular phones and laptop data cards from Cingular can use HSDPA. Its data-centric hand-helds, like BlackBerrys and Treos, are still stuck on EDGE, which Cingular continues to maintain alongside the new faster network.

But Cingular plans to offer new versions of the data devices in the coming months that can take advantage of the new, higher speeds. By contrast, T-Mobile has nothing faster than EDGE. Verizon Wireless and Sprint also have networks that are much faster than EDGE, based on a technology called EVDO. They are way ahead of Cingular in both the number of cities deployed and in the variety of devices that can use the highest speeds. For instance, the Verizon Treo I carry uses EVDO and can download Web pages and email attachments much more quickly than any EDGE device can.

There is a catch. With Verizon, Sprint and Cingular, even if your phone or data device can use the highest-speed networks the carriers offer, they will drop down to a lower-speed network if you enter an area where the higher-speed coverage isn’t available.

I bought a Compaq laptop in January 2005. Now in August it will not turn on. Naturally I only had a one-year warranty. The Geek Squad tells me I need a mother board, and that will cost more than a new laptop. Does Compaq have a history of only lasting a little over a year, or did I get a lemon?

Neither my email from readers nor anything I have read suggests that Compaq computers typically last only a year or so. However, reader surveys published by Consumer Reports and PC Magazine rank the Compaq brand (which is now owned by Hewlett-Packard) at or near the bottom in categories like how often its laptops need repairs and how reliable they are.

In general, I believe that as the factories in China (where nearly all laptops are made) jam more powerful and numerous components into slender laptops, quality and reliability are falling. Even Apple, which ranks at or near the top on the surveys I mentioned, is having problems with some of its newest laptops (and I am not referring here to the burning batteries Apple and Dell purchased from Sony).

Are there any good, effective options for getting an Apple iPod to work with a home speaker system? I guess I’m envisioning a “receiver” that allows an iPod to dock with it.

There are lots of products on the market that allow you to connect an iPod to a home audio system, or even just speakers. They range from simple audio cables you can buy at Radio Shack to iPod docks that connect to speakers or an audio receiver, and even wireless approaches. Apple itself makes a $19 cable and a $39 dock for this purpose and also sells a complete kit, with dock, cables and remote, for $99. But other companies sell similar products as well as self-contained docks.

There are way too many of these to list here, but there are some Web sites that can help you. Apple has a Web page listing some accessories, at www.apple.com/ipod/accessories.html. More are listed at Apple’s online store, at store.apple.com, under iPod Accessories — “Cables & Docks.” Another good source for information about this topic is ilounge.com.

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Because of the volume of email I receive, I can’t routinely answer individual questions by email, or consult on individual problems or purchasing decisions. I read all questions I receive and select three each week to answer in the column.

Write to Walter S. Mossberg at mossberg@wsj.com