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 securing a wireless network, adapters that play the music stored on a PC through a stereo and voice-recognition software.

Last week you advised readers that, in order to stop people from piggybacking on a wireless network using a Linksys router, they should simply set up a password and keep it private. But don’t they need to enable an “encryption key?”

Yes. Most nontechnical folks would consider an encryption key as a kind of password, and that’s the word I used because I always try to write my columns in plain, conversational English. In this case, however, my use of the term may have caused confusion, because there are, in effect, two kinds of passwords on Linksys routers and most other brands of routers. One just prevents strangers from changing the router’s settings. The other — the one to which I was referring — is required to actually access the wireless network. That’s the one that’s technically called a “key.”

To enable the encryption key, use the router’s setup software to turn on security. On newer models, the strongest security system is called WPA, and on older models, it’s called WEP. Once it’s enabled, only people who know the key can get onto your network. There are further steps you can take, like hiding your network’s name (called an SSID) from others, or even restricting access to the network to specific computers with specific identification codes (called MAC addresses, a term that has nothing to do with Apple’s brand of computers.)

For more details, go to Linksys.com, select “Learning Center” at the top of the page, and click on “Network Security” from the menu that appears. And then click on the link called “How to Secure Your Network.”

Is there a stereo that I can buy that can wirelessly connect to my computer and play the same music I play with Apple’s iTunes on that computer?

Yes. If you literally mean a stereo, rather than an adapter for a stereo, the best I know of is called Sonos ZonePlayer 100. It involves a module you connect to your computer that links wirelessly to stereo units with built-in amps in remote rooms of your house. It has a beautiful remote control with a color screen and many other great features.

But it’s expensive — about $1,200 for the starter package, without speakers — and can’t play copy-protected music you buy from iTunes, only music you import from your CDs or other unprotected files. Information is at sonos.com. For much less money, you can also buy adapters that can play the music on a PC, or an iPod, through an existing stereo.

I have been keeping a journal or diary. It is hand written but I would like to make the journal more readable by others. Is there voice-recognition software that you would recommend, so I can dictate the entries?

It has been years since I reviewed voice-recognition software, but Dragon Naturally Speaking, a Windows program, works well. For more information, see nuance.com. And Microsoft’s new Vista operating system has a decent built-in voice recognition system. If you are using a Macintosh, one widely known speech-recognition program is called iListen, but I haven’t tested it. Information is at macspeech.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 using Quicken in Vista, blocking people from piggybacking on your wireless router signal and waiting for Mac’s Leopard operating system.

We waited to purchase our new computer until Windows Vista was released. We now have a new HP Pavilion 9000 and were trudging along the learning curve when we came to a complete halt — there is no version of Quicken available for Vista. Since we use Quicken extensively, we are stuck using our old computer. When can we expect to be able to use Quicken on Vista?

I haven’t tested Quicken in Vista, but Quicken’s maker says it works fine in Vista, though you may have to download and install a free update. According to Intuit, the manufacturer, “Quicken 2007 has been tested with Microsoft Windows Vista, and no known issues exist in the most current release.” The current release of Quicken 2007 is called “Release 4 (R4).” If your release is R3 or below, you will have to download and install a patch. You can find more information by going to quicken.custhelp.com and typing “Vista” into the search box.

I use a Linksys Wi-Fi router in my home. How can I make sure that no one else is piggybacking on my signal?

It’s pretty simple. Turn on the password feature in your router, and don’t tell anyone the password. You’ll usually find the password setting in the installation software that came with the router.

I’m thinking of buying a new iMac, but should I wait until Apple releases its new Leopard operating system? When will that be?

Apple is saying that Leopard, the coming version of its Mac OS X operating system, will be released this spring. Based on past experience, any Mac you buy now should be able to run Leopard fine. In recent years, Apple’s operating-system upgrades have been much smoother than Microsoft’s. So, if you really need the new Mac now, I wouldn’t worry about Leopard.

However, if you can wait a few months, and buy your iMac with Leopard preinstalled, I suggest doing so. For one thing, you’ll save some money, since Apple usually charges $129 for new operating systems. For another, it’s possible that Apple will also improve the iMac hardware, though I stress that I know of no such plan.

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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