I've been meaning to write something like this for some time now, but have always pushed it off. No longer! After a co-worker asked me about a possible fraudulent antivirus software on their home computer, I figure this guide can help many. Or few. Ether way, here goes:
Steve's Guide to Removing Malware, Spyware, Crapware, and Most Other Negative-Wares From Windows Computers*
If a window pops up asking you to pay roughly $60 to install software that you didn't know about, you've got a malware issue. As long as the roots are too deep, you'll be fine.
Here is a list of the main software that I use when cleaning a machine (keep in mind that these are all free):
This application is great in cleaning out primary infections. After install I recommend running the quick scan, then the full scan afterward.