Red Rings Of Death ! :-
Basically, when you switch on your X Box 360, the 'circle' of lights, rotate, and when the controllers are defined, 1-4, the corresponding quadrant lights, will be shown.
The rings of death, happen, when there has been a major hardware error.
They ALL turn RED, and stay on, usually you get NOTHING on screen, sometimes you get a black screen, with ERROR 74, on it.
This is caused by a couple of known hardware issues, that Microsoft has known about for a while, thats why they extended the standard warranty to 36 months _ but that's NO GOOD for all those folks that flashed their consoles !!
The red rings can be fixed, one way is to install a different heatsink, usually a normal pc heatsink & fan, or use what is called an XClamp kit.
Mainly it is a processor overheating problem, but the newer consoles, ie, the Elite, has a different, better cpu, that does'nt suffer the overheating issues.