The DVD drive is tied to the system based on a hex value in the firmware of the drive. If the dvd drive has a mechanical error and you can extract this value, or if YOU/someone you know can extract this value using a chip reader, then you can inject the value into another drives firmware.
For this reason, xbox 360 drives are interchangeable, but its not as simple as just a hotswap. You will have to do some work to have anything more than a simple paperweight.
As long as the person before you didn't blast another firmware onto the chip, you can get that 360 up and running. If they did, then you are basically stuck with a pile of junk, as there is no way AFAIK to extract that info from whereever it is stored on the main system.