no
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.
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.
NO
on some they do
Yes, the XBOX 360 come with the hard drive at new price.
If you mean "new" as in the Slim models, then no.
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.
buy a new hard drive?
no actually it will however you have to do some unscrewing
No, you cannot use an external hard drive on the Xbox 360 to play original Xbox games like Halo 2. The Xbox 360 is backwards compatible with select original Xbox titles, but these games must be installed on the console's internal hard drive or a compatible Xbox 360 hard drive. An external hard drive can be used for storing Xbox 360 games and data, but it won't support original Xbox game playback.
The prices for a 20GB hard drive for an Xbox 360 tends to vary depending on whether it is a new hard drive or a refurbished one. A refurbished hard drive sells for approximately $30 but the prices for a new hard drive can be priced as high as $80.
Any hard-drive for the Xbox 360 arcade, premium and elite will fit into each others. but the new slim Xbox 360's hard-drive is only small and will only fit in othe Xbox 360 slim's Hope i could help! :)