What can i do to force system restore?

2 days ago i turn my pc on and find no start menu, so i hit F11 to no avail, then tried to do a sytem restore but it claims i have to restart me pc first to do so, so i did and retried...didnt work. did an AVG scan of a virus, nothing found. still claims i cant system restore and its not even checked in the option box to disallow system reboots....i really dont know whats going on. command prompt wont even let me system restore.