bhush,
what your asking for basically has one big flaw, the HDD may have to come with an on-board decoder which will decode the movies and send the signals for you to be able to watch it on the TV/ Monitor. If it is a software decoder then you need a processor which can do the decoding. Else you need a H/W decoder. If it is H/W decoder then you still need a processor capable of interfacing with the signals and send the information out. So a HDD with whatever casing is not possible. However you might consider going in for a modded xbox if you wanna do the above. Install XBOX Media Centre and store the movies on the 200gb hdd and have all ur fun....