there is a fix if yours has been modified but its a ball ache

what you have to do is take everyone apart so your down to the mother board etc

then you need to take the heatsink

once this is off you power the machine up until the solder starts to turn to liquid again and turn it off

well thats hw my mates fixes them anyhow i think

and hes repaired about 4 now

as the xbox gets that hot the solder melts and when cools down again there is a crack in the solder joint so it doesnt mae connection hence the 3 red lights

im sure theres a something on the net somewhere to tell you exactly what to do and fix it