Not trying to pick a fight or anything, but let me understand this. He lost his software that allows him to play DVD's? Not a hardware issue? But he needs to replace his drive?
On both of the upgrades that I have done (Win98 to XP, and now Vista to Win 7, and I'm NOT an expert). When the new OS is installed the software that came with the computer from the manufacter to play DVD's/Bluray is/was lost. Luckily this time around, I just went to the manufacter's(HP) website. I looked for my model number, and they had ALL of the former software for Vista as well as the Win 7 versions, for NO cost. I had my Bluray and DVD's playing in no time.
If this doesn't work, then I'm sorry I suggested it.
Ditch