|Get a paper clip, unfold it, look at your dvd drive, there should be a small hole next to the open/close button. put the paperclip in and push, this will force the drive open.|
This obviously is not a fix, its just to allow you to do whatever you need to do.
you have two options
1) chage the belt inside the dvd drive that opens and closes the door (if that is the problem - usually is)
2) buy a new drive.
i would probably buy a new drive.