I used to always use avast and windows firewall because it was good enough. But now norton makes an upset and came out with norton 360 which pwns avast. Sad, avast is free yet its better then a lot of payed AV's.
Norton 360 is very light, especially if you disable real time scan, it has a auto form filler, and it remembers all of your passowrds you used on every site you visit. You can use a master password so only you can get into it. Norton still has a tendincy to pick up on false positives but you can adjust that by lowering the protection to low.
Norton 360 - can remove tracking cookies
spyware blaster - prevent spyware getting to your computer
malwarebytes - for scanning
RegTweaker - deep registry clean, junk cleaner
uniblue speed up my pc - remove hidden junk files that norton, and regtweaker can't pick up
Tune Up Utilities - good computer maintenance. Also detects junk that all of the above can't detect.