If you have Windows XP or 2000 run this tool: http://siri.urz.free.fr/Fix/SmitfraudFix_En.php
If you have any other Windows (including XP) try the free versions of these two tools and update them before running. Let them remove anything they find and reboot if asked to.
http://www.superantispyware.com/superantispywarefreevspro.html (except for Windows 7 32-bit, use the one below)
I moved this to Malware Discussions by the way.