There are numerous possibilities. Potential Failure Modes
includes: (a) Motherboard (b) Cables (c) Hard Disk IDE (e) X-Files
It is quite unlikely that the cable would fail, but guess one would
never know. Sometimes, after one or x days and you try again, the
IDE Hard Disk may be visible again. If this happen, somewhere
between (a) to (e), there maybe this potential problem waiting to
erupt again. If you have an external hdd casing, you can perhaps
verify if the hdd is working on the external casing, using the same
or another computer. cheers, Mr Tan