Before doing a virus scan you should clean out all of your old and junk files first: Goto add\remove programs & de-install everything you don't use, don't like or don't even recognize (Carefull with the last one, DO NOT remove drivers and such. Use Google to search out the progs names) Use an app like CCLEANER to clean your system and junk files also goto tools in your ccleaner menu and select startup and delete the things you absolutly cannot identify or don't want running at startup any longer. Then run a checkdisk (Will require a reboot) and defrag your system. THEN run a full AV scan. Let it run all by itself 50 minutes is a little long but not too suprising for a 4 year old system.