Dan's a geek

Maybe I won't have to re-install Windows after all.

I removed a few items from the StartUp folder, deleted SpySweeper, and forced McAfee to download an updated databank.

Good as new? Probably not, but waaaaaayyyy better than it was.

Update

Though this sounds as if I did all this stuff at one time, it was actually a two-step, at least, process. After cleaning the Start menu and deleting SpySweeper, the computer ran fine for a week or so. Then McAfee started acting up -- repeated warnings that "Your computer is not protected!" After a few days, I went to the McAfee web site, downloaded and ran "Virtual Technician" (no problems found) and then searched McAfee's Knowledge Base until I found these instructions:

Windows XP / 2000:

1. Click Start, Run, type Explorer.exe, and click OK.
2. Navigate to C:\Documents and Settings\All Users\Application Data\McAfee\HackerWatch\data.
3. Delete the file HwLocal.xdb.
4. Close Windows Explorer and restart your computer.
5. Right-click the M icon in the system tray (near the clock) and select Updates.

Problem solved.

(Some "update," huh?)