There is no "absolute best" software.
Nod32 is a decent AV. If you're already using it, keep it. If not, you could use it anyway or consider using AntiVir free, which has slighty higher detection rates at the expense of slightly more false positives.
No matter which AV you choose, I suggest you implement some good security practises. Such as uninstall programs you don't use , keep your software and Windows updated (e.g. with Windows Update on and Secunia Software Inspector), switch to alternate (less popular) software if possible e.g. Firefox/Opera/Iron instead of IE to get "security through obscurity" and always exercise common sense when browsing the web.
You should also keep Windows Firewall on and disable autorun
Also WOT and AVG LinkScanner are great site ratings software. Sandboxes or policy restrictions also provides great protection, e.g. Sandboxie, Returnil, GesWall, DefenseWall or Limited User Account.
Edited by Someones, 28 April 2009 - 07:56 AM.