There are several options here the most obvious is that the drive is the wrong size for the M'Board. Quite a lot of the P2's had an upper limit of 60 GIG on the supported HDD's and without a third party piece of software to [b]Trick[/b] the BIOS into seeing several drives with the upper limit this could be your problem.
There is also the possibility that the IDE Controller has failed which is preventing the drive from being read. I've seen this happen several times recently on High End P2/3 Dual Processor M'Boards.
The Power Supply could be bad and not putting out enough power to run the unit correctly.
You can always try downloading the Drive Makers Testing Utility to test the HDD nd see if it's working correctly. This will test both the HDD and it's controller so if you get a result of a nonworking Drive you need to test it again in a known working computer just to rule out the IDE Controller.
If you can not find the Drive Makers Testing Utility there is always [b]The Ultimate Boot CD[/b] available for download at
http://tinyurl.com/3jnpy
Which will allow you to test the HDD and many other things as well.
Col