QUOTE(neo_on @ Apr 30 2012, 10:23 AM)

I rested the xbox for an hour..booted it up again, this time the drive was in its enclosure and the xbox not totally assembled. It did not last 5 mins - Same half red ring of death! It doesn't make sense - I can't feel a thing heating up in the xbox in 5 mins. Surely looks like POT trick messed up something. My drive had a setting of 5.6 for the POT, so may be 3.1 is a bad setting, may be I should re adjust it to 4.0 or something? Could it be related to POT at all? or Am I better off assembling the console first and then trying it?
Hey, don't worry. An overheating Xbox is much better than any of the other error codes and much easier to fix.
And yeah, the twist magnet mechanism does feel cheap and the amount of force you need to twist it off feels like you're going to break the thing, but I have yet to snap one in half doing that.
For the overheating, the drive would not have affected that. You may have bumped the heatsinks or put pressure on them and squeezed out some thermal compound. Make sure your fans are both running and that the white fan shroud is in place.
You will likely have to:
Take everything out of the Xbox, remove the motherboard, remove the x-clamps beneath the motherboard, pull the heatsinks off, clean the thermal paste completely off of the heatsinks and the chips, replace the thermal paste with Arctic Silver 5 or Arctic Silver Ceramique thermal paste (found online or at radio shack), then put the heatsinks back on and put the x-clamps back on.
It would've been a good idea for you to do this anyway because that xbox is so old and the thermal paste is probably all dried up and gross and not doing its job well anymore. If you decide to try this I have a few tips. When trying to get the x-clamps off, although they may be easy to get off because the xbox is old, try not to scratch the motherboard at all while removing them. Once you pry two of the 4 ends of the x-clamp off, you can usually slide the other two off without tools. And for reassembly, then snap back on, but make sure theyre all the way snapped. You only need a verrrrrrrrry thin layer of thermal paste. It just need to cover the metal surfaces of the chips (2 on the GPU and 1 on the CPU).
And on a side note, try to refrain from turning the 360 without the DVD drive plugged in, as people have reported being banned from Xbox Live for this.
Let me know if any of this baffles you.