|Download & run HijackThis.|
You should also scan for viruses & malware. This should all be done from Safe Mode. You might also want to temporarily disable System Restore, but be aware that in doing so, ALL restore points will be lost.
Which antivirus program are you using? AVAST, AVG, & Microsoft Security Essentials are totally free. Malwarebytes AntiMalware & Hitman Pro also have a freebies available.