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.

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 antispyware software, Powerline adapters and the Mac mouse button.

I set my parents up with a new Dell PC, and included antispyware software that I run periodically to clean up the computer. I recently discovered they had more than 200 instances of spyware on the machine. This may be because my 81-year-old father surfs porn sites ALL the time (this isn’t a joke). Is there any way to keep his computer bulletproof and safe?

Assuming you can’t dissuade him from the porn sites, which are common sources of spyware and adware, your best option is to switch to a type of antispyware program that blocks the installation and operation of spyware and adware programs as it is happening, rather than waiting until they are installed to clear them out. The best program I have tested of this type is Spy Sweeper from Webroot, but there are others. These types of programs usually aren’t free, but their prices are modest and they would allow your dad to spend his golden years as he sees fit.

Last week, you recommended Powerline adapters that can route an Internet connection over the regular electrical wires in your house. I have two questions about these products. If a home has two different circuit-breaker boxes, can adapters plugged into outlets connected to the different boxes communicate? And, could a neighbor who shares an outside electrical line potentially spy on my Internet usage?

I am not an expert on electrical systems, and neither of these circumstances applied to my tests. So I asked Netgear, the manufacturer of the XE104 adapters I reviewed last week.

The company says that if the two adapters are plugged into outlets that are on totally independent electrical “loops,” they won’t be able to communicate, because the electrical current itself wouldn’t pass between the loops. However, Netgear claims it is “extremely rare” for a home built after 1950 to have two wholly independent loops, even if they have two different circuit-breaker boxes. The company says that, at least in newer homes, separate circuit boxes are often linked.

However, I would add that electrical layouts vary so much that there is no guarantee that any two electrical outlets will have a connection that will work with Powerline adapters. I believe it will work in the vast majority of cases, but not all. In my home, which is 36 years old, the adapters did work between rooms with different circuit-breaker boxes.

On the security issue, the company says it is theoretically possible, but very unlikely, for a neighbor on your same outside electrical line to spy on a network running over your interior electrical wires. To do so, Netgear says, the neighbor’s house and yours would have to lack a filter between them, and those are commonly present. Even then, a nosy neighbor would have to know that you have a Powerline network — and buy a compatible adapter — in order to access your network.

This is likelier, but still not very probable, in an apartment building, because circuits in such buildings are often shared. The company does include optional encryption software for such situations, so that even if a neighbor can snoop on you, he wouldn’t be able to decipher your network traffic.

I am thinking of buying an Apple MacBook, but I notice it only has one button below the touch pad, and no obvious scrolling control. Without buying and using a mouse, how can you right-click and scroll on a Mac laptop?

The Mac operating system and Apple software do in fact support right-clicking, displaying the same sort of pop-up menus that Windows does. However, on a Mac laptop with the single button, the traditional method for right-clicking has been a clumsy one: holding the Control key while clicking the button.

Now, the latest Mac laptops have a much easier and cleverer method for right-clicking: you just place two fingers on the track pad and click the button. It’s fast and easy, though still not as good as if Apple abandoned its odd mouse dogma and simply built dual buttons into its laptops.

Also, the new Mac laptops have a method for scrolling that I find superior to the methods common on Windows laptops: you just place two fingers on the touch pad and drag them up or down together. It quickly becomes second nature.

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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 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