If the reason that you are looking for a new anti-virus is the cost, then you may want to check out http://www.free-av.com/ I have used this free anti-virus program on many of my personal machines and found it to be a great peice of software. I don't know how well it fullfil a corporate environment's needs. (For anyone considering that.) It is much less resource intensive than Norton Antivirus. (Not to bad mouth Symantec but their utilities lately have been pretty resource intensive. )
Try the Anti-Virus from , it comes with a professional Anti-Spyware and updates itself automatically (free for 1 year) and it scans in the background - using less resources than most!
If it finds a virus it brings up a hazard sign and a siren sounds - v cool :-)
I use it because it managed to install on my infected PC (when Norton and McAfee wouldn't) and it found the virus straight away plus it has kept my PC clean since. Get it at or
Hope this helps!