Download, install,
UPDATE then run both Spybot (
spybot.info) & Ad-Aware (
lavasoftusa.com).
Next download
CWShredder, save it in your desktop, close your browser & all other open programs before running it, & let if fix what it will. (By the way, the CWShredder project has been suspended at v1.59.1, but it removes quite a few common hijackers made up till very recently).
Reboot, & if you're still having problems, post a log generated by
HijackThis and someone here will be along to help you further.