Run this free online scan app first to see if you have some serious infections.
http://www.webroot.com/services/spyaudit_03.htm
If so, I recommend downloading the trial version or paid version of Spy Sweeper 4.0 and clean out all the malware.
http://www.webroot.com/consumer/products/spysweeper/
My son's PC had 5 ad ware programs that none of the other progs could fully elminate. Spy Sweeper 4 identified them all perfectly and cleaned them all out in one quick run.
This is the most effective program I've used and highly recommend it.