not sure what you mean, but firs off you don't' need lots of background apps running to keep you safe.
anti virus = nod32 very light low CPU
firewall Sygate pro very light low CPU
anti spy ware = spysweeper run it only once a week for cleaning.
that is it very light, and low CPU
thats my setup and I do lots more then all of the stuff you are talking about.
if you really want a good setup to be able to do stuff freely its your ram not how you setup the PC.
you got a c2d how much ram you got with that?