In addition to what bhankiii said, download free versions of AdAware 2007 from Lavasoft.com, and Spybot Search and Destroy from Safer Networking.
You might also consider running AVG Free Edition from Grisoft.com. I have it and it is pretty good for a free program. It updates almost every day, and it has popped up with "Threat Detetected" messages at times.
You can find links to all these programs at www.komando.com, and clicking on the security center button.
If these programs don't help, then look around on www.pchell.com to see if there is a solution for the specific virus you have.
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I wonder..... Would Schrödinger's cat play with a ball of string theory?