If you have a red ring of light around the power button, then your cause is RoL, and microsoft will estimate and possibly repair for free. go to the xbox microsoft website, support, and register your console. you can figure it out from there.
if you have no RoL, and an error message displays on the screen, the next most likely culprit is your dvd drive. again, send to microsoft for a free estimate. they even ship a box to you. most frustrating part is registering your information and describing the problem.
friend wrote two days ago, "RoL! AGAIN!! IT HASN'T EVEN BEEN 45 DAYS!!!" referring of course to the fact that is console was repaired and returned once already.
gEORGE sNITZ, June 2008