If you are thinking about putting a PC into an actual NES, then I actually have experience with that. You will have to make compromises if you want to keep the original outside. You won't be able to fit a standard PSU in the case with a MOBO, GPU, and ODD. I can get actual dimensions later, but the base of the NES tapers in and provides more limits to what you can do. You will also have to cut a lot of the inside out and make the base completely flat to fit all of that in there. My suggestion would be, if you are looking to put a PC in an actual NES, determine what is most important and what you want to use this PC for. Without HEAVY modification, you will be limited as to what you can put in there and still have acceptable performance/cooling/noise.