also, it may not be a virus, but 'malware', a background download by going to the 'wrong' page. I have c(r)ool Web Search stuck on my machine. Here's how bad it is..
It downloads itself to your System32 directory as a randomly-named dll file, and executes on startup. I creates registry entries to change your home page to 'about:blank', then puts a few others in there as well. If you use anti-spyware, it randomly re-names the dll. I have the following running; Spybot, Add-aware, CWShredder, Spy Sweeper, Killbox, and the score is Cool Web Search 1, all other programs 0. It finally 'killed' IE altogether, so I use Mozilla now. I got IE back, but it immediately became infected again.
This is how they work..why do a virus, when you can @#$% up someones' machine so much more effectively this way...rant over..;)
Most of the above programs are free, and frequently updated. You can fight some of this stuff to a draw, but I wouldn't be surprised if I have to reformat the Hard drive to get rid of it..so far, I'll just use mozilla (which is free, too)

I wish I'd said that.. The Staircase Wit

anahl nathrak uth vas betude doth yel dyenvey..;)