When you update your BIOS, it overwrites the actual CMOS chip on your motherboard (the physical hardware). Not on the C:\ drive or such. It's possible for an error to have occurred when your friend flashed his BIOS, therefore resulting in an unusable computer.

Go to the website of the motherboard manufacturer and download the latest BIOS flash update onto a floppy. Have your friend run it via DOS and hopefully it'll fix the problem.