Wanting to turn an Atari 800 into a modern gaming PC

So I have this http://i.imgur.com/CpAZFT7.jpg Atari 800 that I have been wanting to turn into a gaming PC for my wife to play on, and I have no idea what I am doing with it. I was hoping all of you in the community would be able to give a first timer some advice or have some links to others who have tried this so I can get an idea of what I am doing. If there is anything you can help with info wise I would greatly appreciate it.

Take some measurements and see if an itx board will fit.

I know a Mini ITX board will fit.

What type of connector does the keyboard use?

well gut it.

Show us how it looks inside, you may need to drill, cut and glue a lot... also you might need to get rid of the built in keyboard and insider your own in spaces. I recommend some cheap usb one to fit in.

I have no idea I plan to take it apart soon and then I can post the dimensions and pics of what the guts inside look like.

I'm not really experienced with case modding, but I think heat dissipation might be a serious issue with that, especially with the thick plastic. You could always through in a low end processor like an Intel Atom , Tegra K1, or Raspberry Pi 2, but that probably won't meet your gaming needs. What are your plans on cooling the board inside?

That was an issue I have yet to figure out.

thats no problem, you could use amd's APU and cut out hole for fan.

That would be pretty noisy with a stock AMD fan haha. Maybe swap that out with a low profile fan.