Owners of any Mac with an Intel processor—about 80% of all Macs in use, including yours—will be able to do simple, direct in-place upgrades to the new Snow Leopard edition of the Mac operating system, due out soon. This method will preserve all programs, files and settings without requiring any of the hard-disk wiping, temporary offloading of files and re-installing of programs that Microsoft is requiring to move to Windows 7 from its most popular current version, Windows XP.

Not only that, but Snow Leopard will cost you and other Leopard users just $29, which is $90 less than the Home Premium version of Windows 7. Apple also is claiming that the upgrade will be up to 45% faster than in the past and that it will actually free up an additional 6 gigabytes of hard disk space.

However, that doesn’t mean there won’t be obstacles or issues for some Mac users. Most important, owners of the other 20% of Macs, those whose models use older PowerPC processors—like the G4 and G5—won’t be able to use Snow Leopard at all. It’s the first Mac OS version that runs only on Intel-based Macs. So, if these folks want Snow Leopard, they’ll have to buy new machines, even though some of them bought their Macs as recently as 2006.

Also, although Intel-based Macs running the older Tiger version of the operating system can be directly and simply upgraded to Snow Leopard, Apple is officially requiring their owners to spend more for it. They have to buy Snow Leopard as part of a $169 boxed set that includes other Apple software they may not want.

Given the manual process of moving from Windows XP to Windows 7, isn’t it likely that there’ll be some third-party utility to handle it?

Yes. Seattle-based Laplink Software has announced that it will issue a new version of its PCmover utility—mainly sold for transferring data to new PCs—that will be able perform automated in-place upgrades to Windows 7 on an existing Windows XP machine, including the preservation of programs. I haven’t tested it yet, and can’t swear that it will work properly. More information is at laplink.com under “Latest News.”

Can you recommend software to remove trial/craplet programs? Something suitable for average users?

The one I have used with success is called “The PC Decrapifier,” which removes unneeded trial programs, add-on programs and advertising come-ons known as “craplets.” The software is free at pcdecrapifier.com. Note that it works only on PCs running Windows XP and Windows Vista. Before you use it, make sure to read the list of exactly what it removes, which is on the Web site.

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.

After reading your positive review, I downloaded Firefox 3.0, only to discover that some of my favorite add-ons, including a search toolbar, are incompatible. What can I do about this?

Wait. As I noted in the review, when major new versions of Firefox come out, it takes a while for some of the many add-ons for the browser to be updated so they are compatible with the new version. Because these are written by a very large number of different companies and individuals, the process will be gradual, and some will be updated more quickly than others.

As for search toolbars, like those from Google (GOOG) and Yahoo (YHOO), I doubt that most people still need them. When they first came out, these toolbars provided things the top browsers lacked: a permanent search box, pop-up blocking and a few other useful features. But all the major browsers now provide these things without requiring the installation of any external toolbar. The companies that make the toolbars can use them to sell advertising or attract you to their search engines. But, for many users today, they are redundant.

I don’t want to run antivirus software constantly, but I would like to periodically run a program that could scan my computer and remove viruses and the like. Does such a program exist?

Yes. Here’s one example. Microsoft (MSFT) makes a small, free program called the Malicious Software Removal Tool that looks for, and tries to remove, a limited number of the worst examples of malicious software. It can be downloaded at www.microsoft.com/security/malwareremove.

However, this isn’t a comprehensive antivirus program. Microsoft says it detects and removes only “specific, prevalent malicious software,” and advises that “You should also use up-to-date antivirus software to help protect your computer from other malicious software.”

I am in the market for a laptop. I was considering a Dell (DELL) or an H-P (HPQ) but have learned that Apples now run Windows. I have financial (Quicken) and other business files (Excel, Word and PowerPoint) that would need to be transferred to the new computer. Would this be possible on an Apple (AAPL)?

Yes, in the same ways you could transfer files from one Windows PC to another. For example, you could burn them to a CD or DVD, copy them to an external USB drive, or transfer them over a network or via the Internet. In fact, if you buy your Mac at an Apple retail store, the store’s staff will move your files over free, or for a modest fee, depending on which folders, and how many, you want transferred.

Once the files are on the Mac, you can either use native Mac programs to read and/or modify them, or you can install Windows and run your usual Windows programs to handle the files.

For instance, even if you never installed Windows on an Apple, your Excel, Word and PowerPoint files could be used in the Mac version of Microsoft Office. However, the Mac version of Quicken isn’t as compatible with the Windows version’s files. So, for Quicken, I suggest installing Windows on the Mac and running the Windows version of Quicken.

• 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.