AVG anti-virus tells me that there is a virus in my asyncmac.sys. I tried to overwrite it with a copy of asyncmac.sys from another computer (making sure that it was the same version of Windows XP, but I was still nervous that I was going to break something), but when I reboot, I get the same virus warning. If I try to delete the file Windows (or somebody) automatically and immediately puts it back. I get a blue-screen death if I try to boot in safe mode. I tried to do a system restore to before I had the virus, but it tells me that it can't restore because nothing has changed.

Any suggestions on how to fix this?