Question: I own a laptop with Windows Vista and a desktop PC with Windows XP, and I'm considering changing both to Windows 7. Is there an online "how to" site for making these operating-system changes? I understand the Vista change should be fairly easy and the XP change will be quite complicated, so I'd like a site where I could read about the procedures and print them out.

Answer: The conversion from Windows XP to Windows 7 isn't easy because XP and Windows 7 are too different. Instead of a simple upgrade, you'll need to do either a clean (wipe out everything and start over from scratch) or custom (wipe out some things) installation of Windows 7. For details about converting to Windows 7 from XP, see tinyurl.com/yfth7a9.

To avoid losing your data during the Windows 7 installation, be sure to back it up to an external hard drive or flash drive. Microsoft offers a free program called Windows Easy Transfer that can help transfer your XP or Vista files and settings to an external drive. See: tinyurl.com/n2zoz6.

Programs cannot be backed up and will have to be reinstalled.

The upgrade from Windows Vista to Windows 7 is complicated by the fact that certain versions of Vista can be simply upgraded only to certain versions of Windows 7. For a list of which Vista versions can be easily upgraded to which Windows 7 versions, see the Wall Street Journal's chart at tinyurl.com/kn8t9k.

But if you're willing to go to more trouble, you can install any version of Windows 7. Microsoft says that "if your current edition of Windows Vista can't be upgraded to the edition of Windows 7 that you want to use, you can still install Windows 7 by using the custom installation option instead." But because the custom installation doesn't preserve your files, programs, or settings, you'll have to back up your data and reinstall your programs as you would with the XP to Windows 7 switchover. For details on custom installation: tinyurl.com/yk6flpw.

Q: I had a trial subscription to a PC clean-up utility called Dell PC Tune Up that I got from Dell with my new computer and service subscription. The trial expired, and I haven't found anything nearly as good that's free. Do you know of any free clean-up software that works to purge or shred files and perform other clean-up operations that enhance PC performance?

A: I searched at www.download.com for "PC clean up" found several free utility programs, including Glary Utilities, CCleaner and Wise Registry Cleaner.

I haven't used these programs myself, so I can't vouch for them.

Steve Alexander covers technology for the Minneapolis Star Tribune. Readers may write to him at Tech Q&A, 425 Portland Ave. S., Minneapolis, Minn. 55488-0002; e-mail: steve.j.alexander@gmail.com. Please include a full name, city and phone number.

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