you can also open the cd/dvd rom drive using a paperclip by inserting it into the little pinhole near the cd/dvd tray opening. Push it in gently and it should open the tray about an inch then gently pull it the rest of the way open.
You might also want to purchase a cd/dvd head cleaner on a disk and you may also try cleaning the disk you're trying to use. The new disks are usually the dirtiest. Anytime I have cd/dvd rom problems, I clean the heads and the disk and everything works again.