ADDITION Another way to kill Viruses is to boot in safe mode, which I believe for XP is F8. And then run system restore from safe mode to a point before you had a virus.
This has worked for me twice when my anti virus and spyware failed to catch a trojan.
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"Thin air? Why is it always thin air?
Never fat air, chubby air, mostly-fit-could-stand-lose-a-few-pounds air?"