Hi khingpynn.
These are all Free & reccomended by us, if you use P2P, peerguardian is a good little program that will help stop alot of spam & known bad IPs.
http://peerguardian.sourceforge.net/
SpyBot search & Destroy,For cleaning worms/trojan's , I Run this before shutting down computer. Some worms become active on startup so scan before close. Oh advanced mode n settings should not be used or changed before fully reading and understanding the fax.
http://www.safer-networking.org/en/mirrors/index.html
The last one is a good adaware shifter.
http://www.lavasoftusa.com/software/adaware/
P.S.set them all to auto update Defs.
Peace.