|But was the DVD drive working before you took it to the shop|
If it was, and when you got it back after they re-installed vista then logically they either broke it, or failed to configure it properly and did not check it
Either way, it should have been working when you got it and it is bad practise for them not to test it.
But, if you want to give it a shot the best way to check if it is a configuration error would to be to go to HP's website and check for any drivers/tweaks they provide.
If the drivers are already installed, or they make no difference then it may be worth going into device manager and checking that windows reports that the drive is OK, and that the region settings are accurate (weird things can happen if they are wrong)