Original Xbox FAQ
My original Xbox won't read discs, what do I do?
Start with a good cleaning
If your original Xbox won't read discs it may simply need a good cleaning inside the drive. To start get some supplies ready. Have a few Q-tips, rubbing alcohol, and some kind of compressed air would be good too. A can of keyboard air duster would work as well as an air compressor (If you have an air compressor, don't use more than 50 PSI) Disassemble the console and remove the disc drive. From there remove the outer shell of the disc drive. Start by blowing the disc drive out well, this includes under the disc tray and every nook and cranny you can find. Now take your q-tip and drip several drops of rubbing alcohol on one end. Keep the other end dry and clean. Use the wet side of the Q-tip and lightly wipe across the laser lens, specifically the clear glass part. Then quickly use the dry side of the Q-tip to wipe away anything on the lens. You can also do this on the spindle motor (That's what holds the disc). Now re-assemble everything and test it out. If your original Xbox won't read games after the cleaning, then read on.
Replacing the drive
If you did a good cleaning and still have no results, then more than likely the laser in the disc drive has stopped working. There are a few options for replacing the laser but they are new (old stock) and hard to find. They are also after market parts and are notorious for not working most of the time. Your best bet would be a replacement disc drive for the original Xbox box like one of these. A new drive will definitely read discs and get you back to gaming again!