Norton antivirus sucks cause it lets almost everything through. I use f-prot and its awesome. Also NAV is resource hungry. NAV 04 requires about 15 - 18 mb ram (approx.) Really used to slow down my pc. So i switched to f-prot and it takes about 600 - 800 kb ram and runs 2 files. The autoprotect and scheduler the latter u can switch off.
Go to
http://www.f-prot.com for more. It sayz that the min req. is that u should have a running windoze cause it that works so will this