Automatic restart in Hibernation

Hello, Im sure this has come up before so please excuse my Newbieness.

 

Most nights I put the machine in hibernate only to find the next day the machine has turned itself on and then restarted - as I find I have to recover some of my files after an "unexpected shutdown" or whatever.

 

This is becoming annoying and I suspect its my NIS doing its best to protect me. Im running Vista (still!)

 

Plain advice would be greatly appreciated.

 

(This spell-check is a nice function!)