I just made a topic about a month or two ago about this. Download AVG Free 8.0. It leaves an annoying process that you can't end in the task manager (which eats up anywhere from 5,000k-45,000k of memory), but it works well. Also, download Malwarebytes Anti-Malware.
My comp was pretty much as close to fucked as it could get, but it's perfectly fine now.
Past:'08 E92 335i|ZPP|ZSP|6AT|four (4) HPFPs
Present:'15 Mustang GT|401A|PP|6MT|Recaros
Sig pic unrelated. I like to go sideways and stuff.