I'm guessing you've checked all the electrical connections to the original drive?
When you say that your downloaded application was unable to fix because it couldn't 'read the drive', what do you mean?
Can the DVD drive successfully read any other 'known good' discs (music/data/video)?
Can you see the DVD drive in Windows Explorer?
All helps with a diagnosis, apologies if you've tried all this already and have confirmed the DVD drive is faulty (of course, if it is, Keef and ExXB have offered two possible solutions).