In the recent few month I have come more and more across personal laptops and desktops infected with various rootkits. The standard solution is to wipe the OS and reinstall. Recently an alternative may be a rescue CD with the antivirus software on it which is used to boot the computer and scan the filesystem directly. Of course, this assumes that hackers have not modified the OS with non-standard malware.
The best one so far that I found is BitDefender’s RescueCD which can be downloaded here. A nice feature is that if you plugin a network cable, the CD will download the latest virus definitions before scanning.