What causes a hard drive to not be seen by the BIOS?

I took a look at a "dead" hard drive for a friend today. It's not being
recognized by the BIOS anymore.

Once or twice the drive was recognized OK, and during those times the
diagnostic software I used indicated that the drive had a bad sector 0.

Is the information that a drive presents to a computer's BIOS stored
somewhere as data on the platters somewhere? (I was thinking that the
information was in the firmware of the drive) Could this be a case
where the drive developed enough bad sectors, and because they happen to
be in the sector 0 area, it's not being recognized by the BIOS?

Comments?


-WD