I ended up figuring out how to add\remove hard drives on that computer I
posted about earlier. Like I said, the side panel to access the motherboard was easy to open. It has a tool-less screw that you can unscrew with your fingers. However the rest of the case's cover is a one piece deal that is riveted to the case many times.
However I noticed that there is a green plastic bracket covering the drive cage. The drive screws which usually attach the drive to the drive cage go into some catches there with one screw to firmly secure the drive. Well, I had to remove the front panel of the computer with its latches and slightly pull the catches for the drive and slide it out.
I slid out the hard drive and found out it's an Ultra ATA Seagate U Series 7 60GB hard drive. I can find an 80GB 7200RPM one that should be compatible for about
$34 bucks or
less. So I have bad news for my family but I also have potential good news. Much better than the $80 one I found before when not knowing the exact kind of hard drive it had.
If that doesn't work there's something more serious wrong with the computer such as a bad hard disk controller. If that's the case that computer is ready for the junk pile I'm afraid. I don't think I'd want to have them buy other parts such as a new motherboard, CPU, RAM, etc.
It's a good thing that they don't have anything terribly important on there. Everything in there is going to be lost unless we have a data recovery service performed on it which is probably not worth it.
By the way HP swallowed up Compaq a few years ago and they only have basic support on their site for the Compaq computers from before the acquisition. Things such as archived drivers from the last time they where revised for that computer. The only documentation they have to download is a list of support numbers. There isn't anyplace where I could find specific information like specs so I can find out what type of hard drive it uses. So this was the only way I could find out.