ive had this problem before, and solved it instantly (but it may come back)(happened to me a week after i got it)
heres how
1) turn on xbox, see if it reads disc, listen to it trying to read the disc, it may not make any sound.
2) take out disc, KEEP DISC TRAY OPEN, unplug xbox from the mains (don't shut it down because the disc tray will close)
3) get out the hoover, put on the small bit thats used for small areas, hoover every hole visible until you feel happy (but make sure that theres nothing loose inside first, i also recommend taking off faceplate for old 360 users)
4) plug back in, turn on and insert disc, problem should be solved
why does this happen? heres why (dust particles cover your laser and stop it from reading discs, and they also stop it moving thats why if you listen there's no noise when it doesn't work)
I am not held responsible for any further damage!