QEvery time I try to update my copy of Windows XP, I get the same strange error code: "800C0008."

AThis could be a sign of a few different problems. First, if your computer's date and time are off by more than 100 days, adjust them and try running Windows Update again.

Another possibility is that some key system files have been corrupted. Run the System File Checker utility by selecting "Run . . ." from the Start menu and typing "sfc/scannow" to have any damaged files replaced with the backup copies Windows stores in a hidden directory.

If you've severely tightened the security settings in Windows, you may prevent Internet Explorer from logging on to Windows Update. Switch your Internet Explorer security settings back to Microsoft's default level (don't forget to switch back to your own custom settings when you're not using Windows Update).

Or the glitch might lie in your firewall program's options. The quickest way to test this is to enable Microsoft's built-in firewall, disable your own, then try Windows Update.

I ran Norton AntiVirus 2004, but it found some viruses it couldn't delete.

Our reader ran into a file called "IEHost.exe" that could not be deleted by Norton -- nor by any of Windows' usual file-management commands. That's because this virus was still active and running. In a case like this, you'll need to quit it before you can kill it.

Hit Ctrl-Shift-Esc to bring up the Task Manager, click the Processes tab and scroll down until you see "iehost.exe" in that long list. Click the "End Task" button, and you can then delete the file in Norton or locate it with the Search feature of Windows, then drag it to the Recycle Bin yourself. Remember to empty the Recycle Bin afterwards!

-- John Gilroy

John Gilroy of Item Inc. is heard on WAMU's "The Computer Guys" at noon on the first Tuesday of the month. Send your questions to him in care of The Washington Post, 1150 15th St. NW, Washington, D.C. 20071 or via e-mail to jgilroy@iteminc.com.