Hey Clint, it sounds like you've got a bad drive, that problem is fairly common with them especially certain models like the Thomson ones. Here's a good site for reference on Xbox DVD drives:
XBOX DVD DrivesIf you do decide to replace it you can get one from eBay or some other such shop and either put it in yourself or have a shop that does mods put in another one, they can either put in a stock drive or a off the shelf PC one. If you do decide to shop for one yourself use that site and familiarize yourself with the differences between the different makers. Samsung ones are the best followed by Philips and lastly Thomson.
There are also Hitachi ones as well but they are fairly recent so haven't really been documented as well as the others for performance and reliability.
Hope this helps.
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Keith