I doubt he is trying to make an Xbox from a PC, sounds more like he wants to build himself a fancy looking PC !!
Its proberbly easier to pick up a book PC in a black case, these normally sell for about the same price as an equivelant full system, but with a very small foot print.
maybe somthing like this !!
http://www.ecsusa.com/products/sBuddie.html
or
http://www.ecsusa.com/products/bookPC.html