And I think I've found a correct HDD, but I'm really not sure. The old HDD has a big strip of black tape on it to prevent tampering, and it covers most of the info numbers. And when I went to, not only, the Compaq website, but the HDD manufacturer site(IBM/HITACHI), too. And neither had any info for this product on their respective databases.
Here's the link to the HDD that I found.
Any more help would be greatly appreciated