I'm currently working on gutting an N64 to run an emulator inside the original case and need some parts. I was told that HTPC parts might be the best fit for such a small case, I just do not know whats good for a cheap price. It will be running games only so the graphics card must be good. Any help would be much appreciated. I will need every part except for the case.
N64 case is too small to fit any type of gaming system in there. You may be able to run a simple computer in the case, just get a full board with built in CPU and video card. Although you said an "emulator" so I'm guessing to run old games in ROMs? You don't need a good video card for that.
And a power supply for a gaming system will be the size of the N64 give or take, so no room for anything else. For a small system to run old 8-bit games on, should have no issues with a low end CPU and video card.