Q After downloading and installing Webroot Spy Sweeper With Antivirus on our Windows Vista PC, we got a warning that the PC didn't detect an antivirus program running. An HP technician told us that Windows doesn't consider the Webroot program certified to run on Vista. Since Webroot is well-known, why doesn't Windows consider it certified? Should we have any other concerns?

JAN DRIGANS, FRIDLEY

A There's no cause for concern as long as you have the correct version of the Webroot program. Some older versions don't work with Windows Vista because it's a much different operating system than Windows XP.

There's also another compatibility issue to be aware of. There are two distinct types of the Windows Vista operating system, and not all programs compatible with one type will run on the other.

Why are there two different Vista programs? To get more computer speed. The 64-bit version of Vista ("64-bit" refers to the length of the "address" used to store data) can use more random access memory (RAM) than the 32-bit version of Vista. Having more speedy RAM means less use of the slower hard disk drive, which speeds up a PC.

So here's what you need to do:

• If you have 32-bit Vista, use version 5.3 or newer of Webroot Spy Sweeper With Antivirus.

• If you have 64-bit Vista, use version 5.8 or newer.

• If you have either version of Vista, and are using Webroot AntiVirus with AntiSpyware and Firewall, you need to upgrade to version 6.1.

For more details, go to www.microsoft.com/windows/compatibility/Default.aspx?type=Software and type in "Webroot Spy Sweeper With Antivirus".

Q I upgraded to the Internet Explorer 8 Web browser, but now I can't use it to get online. Internet Explorer either immediately closes or gives me a message saying that there was a problem and it must close. I restored my computer to an earlier date four times in the hope that I could undo a bad installation, but it didn't help. I can use the Firefox browser to get online, but I can't get Microsoft software updates through Firefox. What can I do?

HEDY HANSON, MINNETONKA

A Internet Explorer 8 seems to work well for some and cause problems like yours for others.

Microsoft says there are several possible causes. Use Firefox to read about them at support.microsoft.com/kb/949220.

For another view of Internet Explorer 8's problems and promise, see news.cnet.com/my-painfully-poky-week-with-ie-8/.

E-mail tech questions to steve.j.alexander@ gmail.com or write Tech Q&A, 425 Portland Av. S., Minneapolis, MN 55488-0002. Include name, city and phone number.