absolutely avast works well we have used it for quite some time, u need to regester it however it is free for personal use. Have not had any problens since i have been using it and i was before so far evreyone I have spoken to that uses it is quite pleased.
It will Scan your computer for viruses, worms, and Trojan horses it also as all of them do runs quietly in the system tray to give u the protection u need (turn off auto updates if u are gaming tho lol cause it can lag u a bit if it does it in game . I dont because it us usually very fast and I will forget to do it otherwise lol good luck man)

http://www.avast.com/eng/avast_4_home.html


Hope that helps some also look into some anti-spyware if u are not already using it we use spybot or adaware both are free and regualrly updated as is avast antivirus. Hope this helps you a little man see ya round

http://www.lavasoftusa.com/software/adaware/

http://www.safer-networking.org/