News: Bungie to reset Reach Credits at launch
“It’s nothing personal.” Credits earned by gamers before Halo: Reach’s official launch will be removed, Bungie has warned. Bungie will reset Credits earned and any gear bought ahead of the Xbox 360 exclusive’s 14th September launch. “Some of you are playing Halo: Reach a little bit early,” communications man Eric Osborne wrote in Bungie’s forum. Read more…
Halo: Reach Campaign Trailer – E3 2010

What is wrong with a Xbox 360 system if it does not allow you to play Xbox 360 games?

My Xbox 360 system will not allow me to play any of my Xbox 360 video games. Every time I enter one of them, it reads ‘Unplayable Disc’. This applies to them all and from inspecting it, I have not located any major scratches on them or anything really damaging.

DVD drive failure, only covered by the 1 year warranty. You can try cleaning it out with a can of compressed air, it may help a little bit.
Eventually you will need to call xbox support and schedule a repair. If you are no longer covered by the 1 year warranty this may cost $100-$140 to have fixed. BUT when you pay to have it fixed, the 1 year and 3 year warranties start over from the day it leaves the repair center.

E3 2009: Project Natal Xbox 360 Announcement