First step is to download, install, and update both Ad-AwareSE and Spybot Search and Destroy. These anti-spyware applications are extremely useful in ridding your computer of such junk. I would not myself trust the help I received from the very people who foisted malware on my computer.
Once you have run these two applications, then if you continue to have problems, you may post a HijackThis! log in the appropriate forum, where our volunteer team can work with you to eliminate whatever HJT finds. The instructions for submitting a HJT log are found here:http://www.bleepingcomputer.com/forums/t/34773/preparation-guide-for-use-before-using-malware-removal-tools-and-requesting-help/
(as downloading and running Ad-AwareSE and Spybot are part of this process, you will be a jump ahead. Links to both products are found in the HJT instructions).