I would just restore Grub again.
Task B4 or B5 of the last link of my signature refers.
Installer can have bugs too. Don't blame the hardware unless you use RAID.
Leave the Bios alone too because Grub works on data fed by the Bios.
If you want to boot the unbootable make a bootable Grub floppy first using instruction as per Chapter 3.1 of the Grub Manual
and let us know when you are ready.