I am often asked to look at computers that are slow, have popups, or are otherwise acting funny. I switched to Linux several years ago and haven't looked back. That typically means I'm “out of the loop” on the platform. Regardless, this page is an attempt to organize some of the best tools and advice I've seen in dealing with these types of problems.
There is a piece of malware called “System Fix” that masqurades as a virus tool that fixes problems on your computer. But, it hides most of the files on your computer. There are good instructions on how to remove this malware at the URL below.