This is not a full detail tutorial, but I wanted to show you how I fix my Xbox 360. When I got the E74 for the first time I tried to find tutorial how to fix it and what it was. First , it's a overheat from the graphic card. Normal when you see the heat sink they put on it. Anyway I try so many modification, Like add 2 fan close to the heat sink, change the thermal past, add little disk under mother board, heat motherboard with a heat gun, etc...But every time it works only for 2 week and bang , come back again. So I decided to do that big modification, I know that suck, because It's look like a space craft..but I don't have to buy a new one and that still working after 10 month.
Sorry for the writing I am franco :-)
Step 1: The Heat Sink
This is what I put on the GPU (Graphic processor unit) It's a mega big heat sink than I take from a Dell computer. I am pretty sure you don't have to put one that big to fix it, but I take no chance and I use the bigger than I have. I also add a fan on it witch is again not really necessary because this heat sink always stay cold but it's already done so I left it there. So I take the 12 Volt for the fan on the motherboard. I you want to do that just google : 12 volt on motherboard xbox 360 and you will find it. Just verify witch model of mother board you have.