Poohlyi Video chip (GPU) on the XBOX 360 (is it, by the way, about it? Or, let's say, about the XBOX ONE?) - really frequent breakdown on the first revisions ...
but there is usually a symptom - a general system error (the red light on the "on" button instead of green is on) ...
"disk" - there is a DVD with the game or other content that is inserted into the tray ... or hard disk (HDD) ...?
even without a disk in the tray, the system should load into the main menu ... if we talk about HDD, then on XBOX 360 (but not XBOX ONE) it, too, if I know correctly, is not necessary to run the system itself ...
After power on - does the power indicator light up? Does the power indicator light up green? what's on tv?