I am in the market for a new HDTV and the newspaper ads are using terminology that I’m unfamiliar with. Do TVs rated at “720p” provide the same quality picture as those rated at “1080p”?

Technically, the answer is no, but it may not matter. The 1080p resolution is certainly higher, but almost nobody can tell the difference between the same material shown in the two resolutions on TV screens up to around 50″ in size and at the typical distances from which people watch those screens. Not only that, but most sources of video content, with the exception of Blu-ray discs, can’t even fully utilize 1080p. Major TV networks don’t use it yet because it requires a lot of bandwidth.

If you can afford a set that can handle 1080p, you might want to buy it so that you are ready in case a lot of 1080p content one day becomes available. You might also want a 1080p set if you are a videophile; have an enormous screen or a projector that fills a large wall; or if you play a lot of Blu-ray discs and believe you can discern the difference on a typical-sized screen. Otherwise, you could save money by buying a 720p set and you might never know the difference.

In 2006, you recommended a powerline adapter for Internet access by Netgear, the XE104. Is this still a good buy or are there others by now that are better?

I haven’t tested powerline adapters, the gadgets that route computer networks over standard home electrical wiring, since that date. Netgear and its competitors — such as Linksys and Belkin — have, naturally, come out with newer, faster units since then. But I am still personally using the XE104 successfully and feel I continue to get my money’s worth from it. It is still being sold. The newer units typically have greater speed in order to do a better job of streaming video around a home, but they work in basically the same way.

I have a Windows XP system, and things work well with my cable modem in my office. But when I’m on the road using Wi-Fi, I can receive emails, but can’t reply or send out. Any idea on how to resolve this problem?

This usually happens because the Wi-Fi provider is blocking the outgoing email server (called an “SMTP” server) that you or your IT department has set up in your email program. Some providers block all such outgoing servers. There are a number of possible solutions. The simplest is to use a Web-based email service, like Gmail or Yahoo Mail, or the Web-based version of your usual service. If your email is provided by your company, you may be able to access a version of Microsoft Outlook over the Internet that will work.

Another possibility is to ask the provider at the hotel or airport what SMTP server it does allow — usually its own — and enter it into your email program’s settings, if you know how. Yet another option would be to use a data card from a cellphone carrier, which I have found can usually overcome this problem. There may be other workarounds, and I invite readers to suggest them.

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

With the new iPods coming out, how do you deactivate an old one? I think Apple only allows a certain number to be used with an account.

You don’t have to deactivate an iPod if you replace it. The copy-protection rules imposed on Apple by the entertainment companies allow for copy-protected music and videos purchased from the iTunes Music Store to be stored and played on an unlimited number of iPods.

The only “deactivation” iTunes users have to perform is on a computer — Windows or Mac — because the copy-protection rules allow purchased, copy-protected songs and videos to be played on no more than five computers at a time. So, before you replace a computer on which you are storing such purchased, protected iTunes material, you should deauthorize the machine by going to the “Store” menu in iTunes and selecting “Deauthorize Computer…”.

Of course, if you aren’t at or near the five-computer limit, this issue may not matter. It’s also irrelevant if none of the music or videos you play from within iTunes is copy-protected material purchased from the iTunes store. You can happily use iTunes and iPods without buying any copy-protected stuff from Apple. You can restrict your music and videos to those you copy from legally obtained CDs, those you create yourself, or those you buy in unprotected formats from iTunes, or other sites, like eMusic.

I have a printer hard-wired to a desktop computer, but would like it to be available to my laptop wirelessly over my home network. How can I do this?

There are two main methods, assuming the printer doesn’t have a built-in networking port or Wi-Fi transmitter. One method is to buy a small box called a print server and plug it into your router. Then, you plug the printer into the print server, and, with the right software and settings, it will appear on your network and be available to any computer on the network, wired or wireless.

The same companies that make routers, such as Linksys and Belkin, also often make these print servers. The other method is to buy a wireless router that has such a print-server function built-in, with a USB port for connecting a printer.

If I have a laptop with Wi-Fi capability, does that mean I can surf the Web while sitting in a car?

Yes, but only if the car is in range of a Wi-Fi network that is either open (not password-protected) or for which you know the password. And it would only be practical if the car was stopped or parked, since a car moving at normal speed would very quickly drive out of range of any networks you encountered.

A better option, which works even when a car is moving, is to purchase a high-speed cellular wireless modem for your laptop, or buy a laptop with such a modem built-in. These modems, which get you on the Internet via citywide cellular-data networks instead of Wi-Fi, can remain in range for miles. But they require hefty fees, typically $60 a month. And, of course, you should only be surfing the net in a moving car if you are a passenger in that car, not the driver.

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

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 using the Belkin Easy Transfer cable, moving files from a Mac to a PC and backing up a Mac with Parallels virtual machine software.

Last week, you advised using an Easy Transfer Cable to transfer files from a Windows XP computer to a new Windows Vista computer. But what about those of us still using Windows 98 who want to get a new Vista machine?

The Belkin Easy Transfer cable I discussed only works fully when the old PC is running the latest version of Windows XP, although it will work partially with Windows 2000. But there are other methods for people using older consumer versions of Windows, such as Windows 98 and Windows ME.

You can, of course, use a two-step process, copying your files to recordable CDs or to an external hard disk and then inserting the CDs into the Vista PC, or attaching the hard disk to it and moving the files over. You could also use a USB flash drive in the same manner. Or, if you are skilled at networking, you could move the files over a network.

However, there are also some cable solutions that will work with Windows 98 and Windows ME. For instance, the Tornado, the cable with the built-in manual file-copying software I discussed last week, works with versions of Windows back to the SE edition of Windows 98, though you need to install driver software for that version. More information is at www.thetornado.com.

Another product I reviewed last week, PCMover from LapLink, also works with older versions of Windows, albeit with different cables that LapLink sells, not the Easy Transfer cable. Information is at laplink.com. Another similar product that has worked for me in past tests is IntelliMover by Detto, at detto.com, which also comes with cables.

I am a Macintosh user and plan to buy a new Dell with Windows Vista. How can I move my programs and files from the old Mac to the new Dell?

Well, first of all, you can’t switch your Mac programs to the Dell. They won’t run on Windows. But nearly all of the common files used on a Mac, such as Microsoft Office documents, text files, pictures, songs and Adobe PDF files, will work fine on your Dell.

I don’t know of a simple, integrated cable-and-software solution for such a Mac-to-Windows migration. So you’ll likely have to use recordable CDs, or an external hard disk or USB flash drive. Just make sure to use drives that are formatted for Windows. Macs can read, and write to, such Windows drives, but Windows PCs can’t natively read, or write to, Mac-formatted drives.

I have a Mac running Windows via the Parallels virtual machine software. I am also running an older Windows PC, which I back up to an external disk drive. Can I plug the external drive into the Mac and copy the files into the Parallels environment?

Yes. A virtual Windows computer running on a Mac behaves just like a regular Windows computer, so you can indeed plug in an external hard disk and copy the files over. In addition, as I mentioned last week, the forthcoming new version of Parallels includes a utility called Transporter that will move the entire contents of a Windows PC into a virtual Windows machine running on a Mac. See parallels.com for details.

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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 recording features for newer iPods, saving files to “write protected” floppy disks and choosing the right cellphone service for your business.

If you have a question, send it to me at mossberg@wsj.com, and I may select it to be answered here in Mossberg’s Mailbox.

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I would like to record my yoga classes on an iPod for playback later, but all of the recording accessories I find work only with older iPod models. Is there a recorder that works with the new video iPods?

Yes. Next month, Belkin will begin selling a $70 plug-in recorder for the video-capable iPods. It’s called the TuneTalk Stereo, and features twin mikes, plus a jack for hooking up an external mike. I haven’t reviewed it, so can’t say how well it works. Another option is to buy an MP3 player with a built-in recorder, like Creative Technology’s Zen Vision: M.

I tried to save a letter on a floppy but received the message that the file couldn’t be saved because the floppy was “write protected.” How do I get rid of this write protection?

Floppy disks have a plastic tab that can be moved up and down to either allow data to be written to the disk, or to block the writing of data, which means the disk is “write protected.” This is intended to keep important files from being overwritten. The tab either exposes or covers a hole in the disk.

The tab is set by default to cover the hole. This allows the writing, or saving, of files. I’m guessing you moved it accidentally, so the hole is exposed, which protects the disk. To correct your problem, turn the disk over to the back, and look for the tab in the upper left. Move it to the position that covers the hole. You should now be able to save your file.

Our growing small business in Pasadena, Calif., is struggling with our decision on the right system and device for cellular phone and email. We are trying to decide between Cingular and Verizon Wireless as carriers and the Treo and the traditional model of the BlackBerry, the one with the full keyboard. What is your recommendation?

On your choice of carrier, I always suggest people decide based on coverage and reception in their home area, their office area and the areas to which they travel. Price and phone selection are important, of course, but they make little difference if you can’t get calls or email where you need them. So ask around and try and determine which one has coverage and reception where you want it.

On the devices, I generally prefer the Treo, which has a much better calendar and address book, and other features the BlackBerry lacks, including a camera, strong multimedia capabilities, the ability to edit Microsoft Office documents and a vast trove of third-party software. However, when you set up the BlackBerry server to work with the BlackBerry devices, it is a powerful email tool and an adequate phone.

One thing to note: Verizon Wireless has much faster data service than Cingular in most cities. The Treo 700s sold by Verizon Wireless use this faster service, and are more advanced than the older Treo 650 model sold by Cingular. The BlackBerry 8700c sold by Cingular is the best full-keyboard BlackBerry model, but it’s much slower than the older BlackBerry 7250 sold by Verizon Wireless, because of Verizon Wireless’s faster network.

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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 mixing Macs and Windows computers on the same wireless network, setting up video-conferencing and switching email addresses.

If you have a question, send it to me at mossberg@wsj.com, and I may select it to be answered here in Mossberg’s Mailbox.

We have two Windows PCs on a wireless network controlled by a Netgear router. We are thinking of buying an Apple Mac laptop. Can the Mac connect to this wireless PC network?

Yes, you can easily mix Macs and Windows computers on the same wireless network, even if the router isn’t made by Apple, and even if the router maker says it doesn’t “support” Macs — which merely means the maker won’t help you connect them. Apple uses the same Wi-Fi wireless standard the Windows guys do, so it can recognize and connect to any standard wireless router, right alongside your Windows machines. In fact, connections are generally easier to establish on the Mac, which had Wi-Fi before Windows computers did.

You can also do this in reverse. You can add a Windows PC to a mostly Mac wireless network being run off an Apple router. I have done it both ways. In my home, I have a mixture of Windows and Mac computers running on a Belkin wireless router. In my office, I have an Apple router that is mainly used with Windows machines that visitors bring in. No special knowledge, special equipment, or special software is required for such mixed networks.

I want to be able to see and hear my grandchildren on my computer. What equipment do I need to accomplish this?

Assuming both you and your grandchildren have Windows computers, you would need to buy and install Web cameras on each. I recommend Logitech cameras, which are decent and inexpensive. Then, you would have to join an instant-messaging service that has video, like AOL, Yahoo or MSN. Then, you just initiate a video session with the grandchildren, and you’re in business. (If you have trouble doing any of this, the grandchildren can probably set it up for you on their next visit.)

Another interesting video-conferencing service for Windows users is Paltalk, at paltalk.com. Skype, at skype.com, also now has a video-conferencing service, for Windows users. If you and your grandchildren have the latest Macintosh desktop computers, both the cameras and the video service are built in, and the video experience is vastly better than with AOL or Yahoo or MSN.

I want to quit AOL, where I’ve been for years, but I need an easy way to move over my address book, forward my email for awhile, and notify everyone of my new address. Does such a thing exist?

Yes. To notify everyone of your new address, move over your address book, and generally to help with the switch, try a service called TrueSwitch, at trueswitch.com. It costs $20, unless you’re switching to MSN, AT&T or SBC/Yahoo, in which case it is free. TrueSwitch will even copy your saved emails, Web bookmarks and calendar entries. I have tested it, and it works, though only with Windows computers.

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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 completely erasing a PC, installing Verizon’s Fios Internet service, and using a Firefox Web browser on an iMac.

If you have a question, send it to me at mossberg@wsj.com, and I may select it to be answered here in Mossberg’s Mailbox.

I am giving my PC to my sister and I would like to completely erase my files from the hard drive. How can I do this?

What you need to do is wipe out the files in a way that is more thorough than merely deleting them in the standard manner. This process is often called “wiping” files, and makes the files impossible, or at least very difficult, to recover. It works by overwriting the portion of the hard disk formerly occupied by a file’s data with nonsense characters.

You could format the disk, but that also would wipe out the operating system, which would require your sister to buy and install a new copy. So you need a program that wipes out only the folders and files you target. On an Apple Macintosh, this capability is built in. You just move the files to the trash and then select “Secure Empty Trash” instead of the usual “Empty Trash” command.

On Windows, you need add-on software. There are many programs that do this, but one that I have tested and can recommend is Window Washer, which is available at webroot.com for $30. You can find others by doing a Web search for “file wipe” or by doing a similar search at download.com.

If you install the new high-speed Verizon Fios Internet service you recently reviewed, do you have to upgrade your wireless network?

It depends. Verizon will supply you with either a wired or wireless router, the box that transmits your Internet connection. If your current Wi-Fi network is slower than the maximum speed of Fios, you should take the Verizon wireless router. For instance, if you have the 15 megabits per second version of Fios, but only have a Wi-Fi “b” type network, which works at a maximum of 11 mbps, take the Verizon wireless router and allow Verizon to install it in place of your current one. The Verizon wireless model works on the newer “g” flavor of Wi-Fi, which can handle speeds of as much as 54 mbps.

You also will need to make sure that all the PCs you are planning to connect wirelessly to Fios have “g” type Wi-Fi connections. If even one of them has “b” equipment, it will drag down the whole wireless network to the lower speed of “b.” (This doesn’t affect wired connections to computers.)

However, if your wireless router is fast enough, and you like it, you can keep it with Fios service. I did, because I am using the Belkin “Pre-N” router, which has better speed and range than any “g” router I’ve seen. I just took the plain old wired router from Verizon and plugged my Belkin wireless router into it. Others have dispensed with the Verizon gear entirely, and just plugged the Fios cable directly into their wireless routers. The main downside here is that Verizon says the routers it installs contain special software that can help diagnose Fios problems.

Can I use the Firefox browser on my iMac? I am running version 9.1 of the operating system.

Unfortunately, no. While Firefox works on the Mac, it requires the newer Apple operating system, Mac OS X, which was introduced in 2001. Firefox requires Mac OS X 10.1, at a minimum. Your computer has an entirely different, older, and much less capable operating system, which Apple has pretty much abandoned.

By the way, for Windows users, Firefox requires Windows 98 or higher. For both platforms, there also are minimum hardware requirements. Firefox also runs on the Linux operating system, and has minimum requirements on that platform as well. Requirements for all platforms are at: www.mozilla.org/products/firefox/system-requirements.

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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