some of them were driven by rubber band. make sure that hasn’t broken. also, if it’s not working and just a generic CD-Rom, take it apart and see if you can figure out what is wrong with it. can’t get much worse off than it is. as much as you would think that they would be, they aren’t all that complicated inside. open it up and play around with it. see if you can find anything that the trey is getting caught on. it might be something very simple. just take note of what went where as you remove parts. at least if you don’t get it fixed, you might learn something about CD-Rom drives. just take your time working on it and see if it’s something obvious.
In the event that you should need to replace the drive, just get a 52x liteon cd-rom from www.newegg.com. it is a good drive at a low price.
hope you learn something about drives, and hope that you are able to get it working again.