I have an HP Pavilion N3110. I had problems finding an HDD for it .(It had 4gb)
So, what worked for me, was to install a 12gb Toshiba HDD. The difference in the two was the way they plugged in. The Toshiba was "offset" by about 6 pins. So I carefully removed the bracket (that thin piece of metal that frames the HDD and has the plug on it), and took the other one off too, and switched them. It's only a few screws and some finesse. The result is what I'm using right now...an HP Pavilion laptop with a Toshiba HDD! There were no other formatting issues when I installed the software. I did remember to write the CYLinders, Heads and Sectors down, and the disk size, large block mode or not, etc... so that I could configure the new HDD.
I don't suggest this for anyone who hasn't handled hardware installations before, but it can be done, because I've done it.
Getting burned in one battle does not mean that you've lost the whole war---Keep swingin' anyway!