Inside of the Xbox.
You can buy a Xbox 360 s hard drive from the Xbox website.
Yes you can
No, the new xbox 360 slim basically has a hard drive like a block, way better than the original xbox 360's long hard drive.
Nothing should happen because you shouldnt been modding the hard drive section, or the hole xbox.
Xbox 360 Elite features a 120gb hard drive and the Xbox 360s features both a 4 and 250gb setup. So the answer is both but the Slim has the capability for a bigger hard drive.
On the Xbox slim No On the Old Xbox 360 Yes
no it is not
I believe that the 4 gb xbox 360 you are talking about is the new slim. There is no way to use your old hard drive with the new slim xbox. You will need to buy a transfer cable to move your saved games to the 4gb hard drive.
No, they are different sizes.
You can convert your regular hard drive to be compatible with Xbox 360 slim but it will contain you taking apart your hard drive. This is fairly easy, the only this you need to do is take apart the hard drive, slide out the main hard drive system and place it into your Xbox 360 slim. There are many videos about this on youtube. It is best to watch tutorials about it before attempting to do it.
Yes! If you open the case on that the old Xbox 360 Hard drive was in, you can just take the hard drive itself out, and put it in the new Xbox 360 Slim.