I think it's really dead this time. . . .

After I concluded that the virus was dead when all the scans came up clean, I did a little research to see why I had a new "HelpAssistant" folder under Documents & Settings, and found that was evidence of a virus infection. I deleted the folder, but it came back again - so I knew I hadn't killed the virus yet.

It ends up it was a virus that infects the Master Boot Record, which is accessed when the computer boots up, and is very difficult to clean. I had to download files to make up a Windows Setup CD (since my computer didn't come with one), and run a utility called System Restore to fix the Master Boot Record. It's tricky, because if something goes wrong with the Master Boot Record, you mess up your entire hard disk. Not good. So first I copied all our documents to my external hard disk, then tried the utility and did the fix. I crossed my fingers and rebooted, and the computer works! And the the HelpAssistant folder hasn't reappeared - let me check one more time. . . . {Pause} Still not there! I think I managed to kill it! Yippee!!