your best plan would be to go into your bios.
disable your ide
secondery master ?
what ever your dvdrom is connected to disable that. then connect it.
that way you will be able to by pass the bios screens and get into dos .....
read here for detailed info on reflashing your drive from dos.
if that dont work then you will have to reconnect the drive when your in dos be CAREFULL doing it this way you dont wanna SHOCK your self.