I would suspect a bad flash first. Which mobo do you have? A lot of companies built in some kind of boot-block inside the BIOS that can't be changed and allows you to automatically flash the BIOS with a floppy with the right BIOS file and some other files, check the manufactuers website for instructions.
Oh, and also try resetting the BIOS.
My dual-PSU PC is so powerfull that the neighbourhood dims when I turn it on