Scratched Discs
The most common error with Xbox disc reading is the result of a scratched disc. This commonly occurs if the Xbox is tipped over during play. Observe the disc carefully. Look for ring shaped scratches, these are the worst and are unrepairable. Minor scratches can be cleaned away. Check the center plastic piece of the disc for cracks. A damaged disc will have to be replaced.
Region Codes
Xbox discs have specific region codes. Discs that are not from the correct region will not respond to the Xbox. Check for the code on the disc. NTSC stands for North and South America, NTSC-J stands for Asia, and PAL stands for Europe, South Africa, India, Australia and New Zealand.
Solutions
Microsoft recommends fixing a disc by wiping it from the center out with a damp, clean cloth. To prevent damage in the first place, store discs safely. When removing discs from their case, push down on the center item so the disc does not bend when lifted. Play with the Xbox lying down so it will not tip and scratch the disc. If all hope is gone, clear the system cache to see if it works. Go to "Memory," select the hard drive, and then select "clear system cache". This will destroy all of the saved data but may fix the problem. Before going to this option, check to see if other games will play. If everything fails, send in the Xbox to be fixed. The Xbox support number is 800-469-9269.