Very good it helps me out and is free, buying the full version unlocks realtime protection, scheduled scanning, and scheduled updating.Clean up that computer!
This one is good as well and is free i use this one also, Both Malwarebytes and this, works great. http://www.superantispyware.com/
Avira AntiVir Personal - FREE Antivirus
I think this free antivirus is better then AVG i use this all the time, it get the job done for sure but don't take by words for it try it out. http://www.free-av.com/en/index.html
SpywareBlaster
Secure your browsers to make it harder for ActiveX programs to run on your computer,Also stop certain cookies from being added to your computer when running your browser works pretty good. http://www.javacoolsoftware.com/spywareblaster.html
WOT - Web of Trust
WOT is a free Internet security addon for your browser. It will keep
you safe from online scams, identity theft, spyware, spam, viruses and
unreliable shopping sites. WOT warns you before you interact with a
risky website. It's easy and it's free. http://www.mywot.com/ X-FIRE