Help Me, Auto Scan's not Working!

My dad got some extra stuff done to the comp, adding in some extra RAM(768 now) as well as a new harddrive(40 gigs). However, we’ve run into some problems-- I had Weatherbug installed like, a year ago with a new version of AIM(sad mistake). So, Dad got Weatherbug disinstalled, causing his mail service to temporarily stop working, and thus had to do a System Restore, since we have XP.
Here’s the bad part: I just logged onto my side, and my Virus Scanner’s AutoScan won’t re-activate! I have no idea how to get it back online. Pleeeeeaaaaaasssse help me, any advice is taken.