Please Click here!, and follow the recommendations in the guide.
If you're still having trouble, We'll need you to use a free diagnostic tool, Hijack This. Follow the instructions in step five of this guide, and reply here with your log.
Most of what Hijack This lists lists will be harmless or even essential, DO NOT delete or modify anything yet! Someone will be along to tell you what steps to take after you post the contents of the scan results.