"Missing" Hard Disk

Since installing Windows XP Pro I have connected the
ATA133 hard drive via an ATA cable to the motherboard. I
needed to re validate windows. More recently and not
connected with this change I am experiencing lock up with
a word document. I have checked and reinstalled Windows
2000 with no improvement. I have tried to re install or
repair Windows but it tells me it cannot find the hard
disk. Other programmes including windows see and use the
hard disk so how do I correct the problem other than re
connecting the IDE cable.

All suggestion gratefully accepted

Steve