Since i know not many will answer your question but here it goes. You need to softmod or modchip your xbox in order to gain new dashboards such as EvolutionX, XMBC and the rest. Also have you opened your xbox yet? cuz that right there will tell you why its so tall. Check out llama xbox parts by googling it so youll know more about the insides etc.
The dvd drive over looks the heat sink etc by using a dvd cradle and the hard drive is located on the other side, and the power adapter is inside also, located on the other side of the motherboard.
Peace.
Wynd