Why would my computer automatically restart after "shutdown" and "sleep"?

This happened to me when I had a bad video card pluged in. I swapped out that card and the problem was solved.

I would recomend removing all add-on cards and usb devices and booting the computer with just a monitor, keyboard and mouse attached. Then if the problem is gone, add one device at a time until the problems comes back. Then you will know which device has a problem.

This was happening to me and i tried evrerything, regedit, and other configurations. i solve it by preesing the clear BIOS button on the board ( the boards that doesnt have the button, remove the BIOS battery for 30 sec.) Trie it, with me it worked.

Ricardo Esteves, From Portugal