optical drive only reads cd not dvd

I am working on my daughters macbook pro santa rosa, and her friend dropped it and it has several problems

the first is it sometimes will not start up when it will not, the only way is to hold the power button until long beep is heard and it will start up. I wanted to run hardware test or do a clean install but that brings me to the second problem.

the optical drive will not read any of the install dvds that i have, I tried a dvd movie and will not read. But it will read a cd. Not much of a help when the software is all on dvd.

Is there another way to find out what is wrong before i start buying new parts?