loading hex code for sd card
Basically you would like to make a slot loading game system?
You're going to do some research yourself. But I'll do some thinking for you.


Your SD-card should have the compiled HEX code, probably along with some kind of checksum? You should check what your PC sends when you're uploading a program (along with the HEX program).
You're going to need 2 AVR microcontrollers and probably some soldering stuff.
Program the "master" Arduino to read the HEX from the SD card. Then make it add the checksum/things you saw your PC sent along. The master Arduino should reset the other ("slave") arduino before sending, just like the PC does, this is done in hardware, and you'll have to wire into the reset button.


I'm not sure if this would work at all. It just sounds like the only possible way.

Alternatively the parallax propellor has a possibility for self-modifying code, along with VGA graphics. This might be a better shot, it's architecture fits better to your project. And I believe there are some similiar projects with the propellor, though I'm not sure about the SD-card.