Use avast with automatic updates + Spyware doctorUpdate ur antivirus and scan ur pc........
May b ur AV hav been disabled/corrupted/bypassed
Scan online(If u r on unlimited plan)
Othrwse install some good antivirus update it and scan.....
Currently running Spybot, Threatexpert Scanner and ad-aware
Install Avira Antivirus Free and do a system scan.
Everyone gives useless advice