[Toaster]

A hard disk controller is pretty much what it sounds like, a controller.
However, the so called "controller" is a misnomer when applied to an IDE/EIDE hard disk because the "actual" controller is actually part of the drive itself.
On system boards, the IDE/EIDE "controller" is really nothing more then an interface for the drive to communicate to the system I/O bus. The actual "controlling" is done by the board attached to the hard disk.
I`m going to hazzard a guess and suggest you recived an error suggesting "hard disk controller failure" while you were working with a PC.
If this is the case, the hard disk and system board are either not communicating or the "set-up" information is incorrect in CMOS.
To verify CMOS set-up, enter your CMOS set-up screen and choose "auto" for the hard disk type and retry.
A persistand hard disk controller error suggests either a cable problem, a power problem or a defective drive.
This error often occurs when a hard disk of too high capacity is used on an early system board which will only support a 8.4GB or an even smaller 2GB disk.