To remove Malware that has already infested your system you may have to run numerous scans using different programs. It is a good idea to have these programs installed on your computer and updated occasionally so that they are ready to use when you need them. Updating them before you perform a scan is essential to ensure that you are able to find even the most recent problems.
Some of the programs that work good for scanning and removing Malware include:
Spybot Search & Destroy . They provide a tutorial for installation and use.
AdAware by Lavasoft. They provide a user's manual.