Why should I format the MBR? Won't that destroy the partition table?
Why yes, yes it will amongst other things. Windows has no issues installing to an unpartioned drive. It will allow you to add the partitions at the same screen where you would pick the drive when you're installing. Just click advanced.
When you get reinstalled, you could atleast check the bios. From your windows based BIOS app (most mobos these days have one), do a backup of the BIOS and compare it to a download from the vendor site of the same version.