Do you still recommend the Dell XPS One all-in-one computer that you favorably reviewed last December? I am not a techie at all but need to replace my 5-year-old Dell and was interested in an all-in-one.

Yes. In fact, I now own two of these Dell XPS Ones and use them as my Vista desktop computers, at home and in the office. I still believe, as I wrote in my review, that this Dell’s hardware is superior to that of the competing Apple iMac, though the Vista operating system is inferior to Apple’s. And the base XPS One now costs the same as the base iMac — $1,199 — instead of $300 more, as it did last year. So, if you want the Windows operating system, and like the look and convenience of an all-in-one desktop, I still favor the XPS One. You can find my review at tinyurl.com/2xw 6mv.

Will Apple’s new MacBooks and MacBook Pros run Windows directly without an intervening “virtual machine” program like Parallels or Fusion?

Yes. All Apple Macs running the current Leopard operating system, including the new laptops, come with the ability to directly run Windows XP or Vista. Using Apple’s built-in “Boot Camp” feature, you can start up the computer in Windows, instead of the Mac’s own operating system, which turns the Mac into a pure Windows machine, with no trace of the Mac operating system running. The upsides of this approach are maximum Windows speed, and compatibility with the most graphics-intensive Windows programs, including games. Note that, to run Windows on a Mac, you must obtain and install a fresh, boxed, full version of XP or Vista. Apple doesn’t supply Windows.

I have a Yahoo email account, and wonder if Yahoo allows receipt and storage of email directly via a computer email program, such as Outlook, or is it all Web storage? Can you do both?

Yes. Yahoo offers a “Plus” option, for $20 a year, that permits users to receive and store their Yahoo email using a locally installed, instead of Web-based, email program. This approach does work with Microsoft Office, as well as many other local email programs. And you can still use Yahoo’s Web-based email interface at the same time. The Plus option also includes other benefits, including the elimination of ads and a doubling of the size limit on individual messages, to 20 megabytes.

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

I bought a Compaq Presario notebook that came with many games that I don’t use. Can I increase the available memory by deleting all of the games?

You can increase the disk storage space that’s available to you by deleting the games, which take up room on your hard disk. But that isn’t the same as increasing “available memory.” Memory is the capacity of the computer to manage data at any one moment, and it is governed by the random-access memory, or RAM, inside the machine. Unless any of the games, or some game-launching programs, are automatically loading into memory when your PC starts up, the games aren’t wasting memory, just disk space. Getting rid of the games is still a good idea, but don’t try to do so by simply deleting them, as you would a file. You should do it by properly uninstalling them using the Windows uninstaller control panel, which is called “Add or Remove Programs” in Windows XP, and “Programs and Features” in Windows Vista.

I plan to buy an Intel-based Mac. I will need to run some Windows software for school. If I use Parallels to run Windows and the Mac operating system simultaneously, and someone does happen to get me with a Windows virus, can that migrate over to the Macintosh side of my computer?

First of all, I can’t stress enough that anyone running Windows, on any hardware — even an Apple computer — should obtain, install and run Windows security software, including antivirus and antispyware software. I do so, not only on my physical Windows computers, but on the virtual Windows computers that run on my Macs via Parallels. Even if you are using Apple’s own Boot Camp solution for running Windows on a Mac, which doesn’t allow the two operating systems to run simultaneously, you should be running security software on the Windows side. Such security software is primarily intended to protect the Windows environment on a Mac. It is unlikely that a Windows virus could migrate onto the part of the computer controlled by the Mac operating system, and even if it did, it couldn’t run there if it was written strictly for use in Windows. It could run only in the faux Windows computer created by Parallels. However, the people who write malicious software are relentless and creative, and it’s impossible to rule out anything they might try, or do. There is one danger to your Mac in this scenario. Parallels includes an optional feature that allows Windows, and Windows programs, to access folders and files on the Mac side of the machine. If you turn on this file-sharing feature, and if you get a virus whose purpose is to delete or corrupt files, it could attack these Mac files, because Windows has access to them. So, for maximum security, I’d advise that you leave this feature off. But, even if you do so, you should still obtain, install and use Windows security software for use when running Windows.

In your column last week about the Ooma device that gives you free domestic phone calls over the Internet, you mentioned that, until the product goes on sale in September, the company is giving away 1,500 free models, but only to people who have been given a special token by existing owners. Can I get one of your tokens?

Sorry, even if I had been sent enough tokens to fulfill the numerous requests I got, I couldn’t fulfill them. I am sending my few tokens back to the company, along with the Ooma gear I was lent for my testing. For ethical reasons, I don’t keep the products companies lend me for review, or take anything of value from them, including tokens entitling people to get a $399 product free of charge. Nor can I help the numerous other readers who asked me to get them on Ooma’s free distribution list.

You can find Mossberg’s Mailbox, and my other columns, online free of charge 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 external hard drives, limiting a child’s computer time and installing Windows XP on a new PC.

I leave my external hard drives turned on and plug them into my laptop when necessary. I use one hard drive to run my manual backup and the other to hold copies of information I want to access, but not regularly. I understand that any hard drive has mechanical components. Am I reducing the life of my hard drives by leaving them running most of the time? My wife says I should turn them on only when I need to use them.

I agree with your wife. Hard disks don’t wear out quickly or easily, so running them all the time when you use them constantly or frequently isn’t fatal. But in your usage scenario, there’s simply no need to keep your external hard disks on all the time since you are using them only once in a while, for specified, manual tasks. By doing so, you are putting unnecessary wear on them and wasting energy. It takes only seconds for them to turn on and become ready for use.

Is there a program for the Mac that would limit a child’s use of the computer to a specified amount of time per day? For example, a parent could permit one hour a day.

Yes, there is. It’s called Mac Minder, and can be obtained at www.lumacode.com/macminder/. It costs $30, but there’s a 10-day free trial. It allows you to set time limits specific to each child, and you can limit overall computer time, or set different time limits for types of programs a child uses. For instance, you might allow one hour daily for games, but two hours for email. You can even set up elaborate schedules governing how long a kid can use certain kinds of programs during particular hours each day (for instance, a half hour of games between 6 and 9 weeknights, but two hours during the days on weekends). The program also allows parents to view a time log of the child’s activities. I haven’t tested this program, so I can’t say how well it works.

I need a new computer but don’t want the new Windows Vista operating system. Instead, I wish to retain Windows XP as my operating system. Is it possible to buy a Vista-equipped computer and then reformat the hard drive and install Windows XP instead?

Sure. But you will need a full, new, boxed copy of Windows XP, not an upgrade version or the version that came with your old computer, or a version that has already been “activated” on another machine. And that may be hard to find. Also, even if you don’t want Vista’s new graphics or other features, be aware that your machine will be less secure, because you will lose some of the new security protections that Vista provides, which are absent in XP.

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