While you are about it, download and install Lavasoft Adaware (the free edition) from
here, then download and install Malwarebytes AntiMalware (the trial edition) from
here (the second one will redirect you to the download site).
Reboot your PC, then start AdAware and get the latest updates, then run a scan and when it has finished, delete everything AdAware finds. Start Malwarebytes AntiMalware, get the latest updates, run a scan and tell it to delete everything it finds (you may need to restart your PC for this to complete).
Your anti-virus program may not detect trojans and the like, but these two programs should clear out other nasties. If you want to, you could also try downloading, installing and running SuperAntiSpyware in case that finds any that Adaware and Malwarebytes miss.