The Xbox 360 most commonly gets the "red ring of death" due to heat cycling. Due to poor analysis by Microsoft's thermal engineers, the heat sinks used to carry heat away from the CPU and GPU were inadequate on early Xbox 360 models. Also, the X-clamps used to hold the heat sinks down against the faces of the processors did not hold them down against the motherboard tightly enough. Because of this, the board would warp slightly when it was heated up near the processors and after many heat cycles they would actually partially de-solder themselves from their ball grid array. Our kit solves this problem by using machine screws to tightly clamp the heat sinks against the processors so they cannot warp.
Fix kit for Xbox 360 consoles with the "Red Ring of Death" (RRoD) failure. Replace, reattach, and reclamp the heat sinks on your Xbox 360. Usually fixes a RRoD Xbox—also effective as a preventative measure. Kit includes: tube of Céramique 2 thermal compou — 10 available at 29.95 each.
I know this is not really the answer to the question, which was only what causes it. This has already been answered.
The kits to repair xbox red light problems can be effective, however usually not for a long time if at all. esp when the xbox is under heavy load. more heat. (big game). The solder points for the GPU and processor are incredibly small like any computer motherboard, it can be very tricky getting to correct pressure to get the xbox to fire up and work properly again.
If your used to working on electronics, doing an xclamp mod on an xbox isn't all that hard.
This is all based on my experience when fixing these things was something I was into, including some serious modding of the original xbox.
They are companies that offer to "reflow" or reball your board which can be successful and work much better, depending on the equipment they have. Usually places on ebay will charge $25-45 to do this...........
So if you figure out how long it would take you to do the repair yourself with a kit, the cost of parts and your time vs paying someone to do it, who does that kid of thing all day, it should make more sense to send it out. (your time = money).