Here's the deal. The hard drive is actually a laptop hard drive in a black case that is made for the new black Xbox 360 Slim system. The laptop drive that is inside the black case can be used in an original Xbox 360, but you must have a case/adapter that allows you to plug it into your older white Xbox 360, this will all depend on how comfortable you feel about taking your cases apart and transferring the HD to another case. As far as the incompatibility with original Xbox games, there's a fix for that too, but again, this is definitely not for everyone as you have to add a patition and some files to the hard drive, I have done this since my purchase and it works like the original HD that the Xbox Slim came with, you'll have to Google this for yourself as I am not the author of any such mods and will take no responsibility, but it most definitely works.
No, it will only fit the slim model, it slides inside the left panel on the xbox 360S. Two totally different designs. However, if you are transferring your stored files with the data cable to this hard drive from the original Xbox 360 it is great.
It has to be an Xbox 360 Slim. If you have a spot on the bottom of your xbox that slides open and looks like a tiny drive would fit in then this is for you, other wise you need the bigger hard drive for the original.