OK, Remoce the CMOS battery and wait a minute or two before re-installing it. US the onboard video card for the recovery.
When you get the BIOS screen up you are going to have to reset the boot order. You may have to format and reload the software to recover the boot sector if it has become corrupted.
Going now to try this!
Boot sectors or master boot records (MBR) rarely become corrupt. If they do you need very specialized software to even get to the MBR and track zero on the drive.
One alternative would be to perform a factory style low level format and then do the logical format. Then you would be installing a generic DOS boot record. He might try FDisk and re install the boot record but better to start all over.
Not trying to be snarky, just FYI
When I reconfigure my machine, I do it in stages, and reboot in between stages so that everything is "comfortable."