The situation is as follows:

There is a 200GB WD ATA-133 HDD. It has XP sp2 installed. It still works just fine when in my standard PC (let's call it PC1). However, in PC2 it just does not load. It is recognized by the BIOS, as well as its full 200GB size. I have formatted a new 40GB HDD in PC2 and it has since worked fine. I have updated PC2's BIOS to its latest version, just in case. I have not tried another HDD with an already installed OS on it. The 200GB HDD would be a primary master in both cases.

Any suggestions?

With respect.