Ok, so I got a free Xbox 360 from a coworker. YAY! The catch? It's a classic RROD. So I said, "No problem!"

and now...

Basically, I went straight for the X-clamp fix. After about 3 hours of hunting down all the tools and parts needed from various shops around town, I tear the system open, remove the heatsinks, clean them and the processors as best as I can (add new thermal paste and all that jazz), and install the new parts. I reattached the power button, fans, and dvd drive and power it on...

Here's where things don't go as planned. Normally, it's supposed to show the 3 red lights again, and you let it overheat the processor under the dvd drive for 20 minutes and then cool down and put everything back in place. Well, instead, I powered it on and it immediately jumped to the dashboard. No RRoD or waiting. So initially I was all "NO WAI! IT'S ALIVE! YAY!". So I powered it off and put all the internal components in the right places and plugged in a controller to test it out. But to my dismay, it RRoD'd again.

After some trial and error I've found that the reason is the processor that sits under the dvd drive (I'm pretty sure it's the GPU) is overheating like mad. Within 3 minutes of turning the cold system on with no RRoD, the heatsink was hot to the touch and the fans are steadily speeding up to the point they sound like a jet engine. I power the system off and back on again and it gives me another RRoD.

So now I'm at a loss.
I can temporarily remedy the RRoD by adjusting the screws holding the heatsinks in place after giving it a chance to cool down, but they just overheat again.

Any suggestions?