Few weeks ago my free version of Avast antivirus detected a virus in the "root directory," I think, so, as recommended, I restarted the computer and the Avast started a scan, but that went so slow I didn't continue at that time. Now, I can't find the way to do this again. The virus does not cause any serious trouble, but whenever I restart the computer, all the cookies get erased.

What do I do? Is any free antivirus that can solve this? I can't recall the name of the virus. Formatting the disc is NOT an option for me at this time.