I wasn't gonna post here since the thread was old, but now that the newbie opened it. I agree, Real-time AV is unnecessary. I use Panda ActiveScan from www.pandasoftware.com once every couple of months and rarely find anything actually malicious.
I take care in what I DL, and I can tell you that I go to sites you are sure to find crap on. I use SP2, have Ad-Aware, but use it as often as Panda, and I have no performance issues that I didn't have upon fresh installation anyways.
A_T
PS - Ratmonkey, you aren't supposed to post in threads that have the dates flashing, that means it's old/defunct.
