I am running windows 7 x64 I have Comodo Internet security (antivirus and firewall) Radeon 4850x2 And it recently started doing this. I have the PC networked to a home server running windows server 2003, and recently changed my login on this pc to match the user I created on the windows 2003 server with which it logs in as. (This negated me having to log in twice- once into this PC and the second to a network share on the server.) I'm not sure if this is significant, but it seems like a networked pc would be less likely to sleep. Things I've tried - I set both display to turn off and pc to sleep after one minute then: Unplugged all USB devices Turned of all System Tray Apps Turned off all Network adapters Picked up a book One minute later the PC's display shut off, but still no sleep. Whats the deal?