Laptop hard drives

[Timothy]

I have two laptops (Compaq Armada 7800 & Dell Lattitude CPi) that might need hard drive upgrades.

I see posts for an IBM 2.5" laptop drive that looks good, but how do I know it'll fit AND work in these laptops? I don't see that IBM posts a list.

Short of buying them from Compaq and Dell at outragious prices (or from someone like Apricot), how can I determine what will work?

Thanks!