I recently reinstalled Windows 7 on a desktop. I used to leave it on all of the time but now I want it to go to sleep or hibernate after a few minutes (and stay that way until we want to use it). I've tried sleep, hibernate, and hybrid sleep. It will power down, but in a few minutes it comes back up by itself. Sometimes it seems to cycle through this, up and down every few minutes.
I've read that USB devices can cause this, but only the mouse and keyboard are attached via USB. There are two internal hard drives.