Q. I use a 1 GB USB flash drive to move files between my Windows laptop PC at work and my MacBook portable at home. But that doesn't work with the 160 GB external drive I use to back up my MacBook; my Windows laptop doesn't even recognize the external drive when it's connected. What's the problem?

A. The disk storage formats used by the Macintosh and Windows operating systems are different. While the Macintosh OS can read both its own file format and the one used by Windows, a Windows PC can read only PC files unless you add some third-party software that enables it to read Macintosh files.

My guess is your flash drive works between the Windows and Macintosh computers because you originally formatted it for Windows - making the flash drive readable by both the Apple and Microsoft operating systems.

Since your original use of the external drive was to back up files on the Macintosh, I'd say it's been formatted for the Mac's OS X 10.5 operating system, and that as a result your Windows laptop can't recognize the drive. To solve the problem, use a PC utility program such as MacDisk for Windows, which allows a Windows PC to read and write in the Apple operating system format.

Q. I'm trying to upgrade my Ad-Aware spyware removal program to the 2008 version, but the install function for the newer version keeps producing error messages. I then tried uninstalling the 2007 version but got more error messages. Can I just delete the old program's file folder to get rid of it?

A. I suspect you can't uninstall the program because it's been damaged. Try reinstalling the 2007 version of Ad-Aware, which may repair the damage so you can uninstall the program in the normal way.

If you downloaded the 2007 program, you probably still have the installer program on your PC. To find it, search your hard disk for the term "Ad-Aware." The icon for the installer file probably looks like a software box or a disk next to a computer.

Completely uninstalling the 2007 version of Ad-Aware is preferable to deleting its file folder. The uninstall function gets rid of all the program fragments that are strewn across your hard disk.

If reinstalling and uninstalling the 2007 version doesn't allow you to install the 2008 version, try downloading Ad-Aware 2008 again to make sure you've got a clean, error-free copy. You can download a free trial version of the 2008 program through www.download.com.

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(Steve Alexander covers technology for the Star Tribune. E-mail your technology questions to tech@startribune.com or write Tech Q&A, 425 Portland Ave. S., Minneapolis, MN 55488-0002. Please include a full name, city and phone number.)