I've got a few purchased video DVD's that when I insert them in the Mac Pro (Feb 2008 model), it spends a minute spinning the disc and then ejects it. Other discs work fine, and these problem discs work fine in my MacBook Pro. Could this be a faulty DVD drive or some form of copy protection? If it could be a faulty drive, will Apple send me a replacement to fit myself. I don't want the hassle of lugging my Mac Pro to an Apple Retail Shop or to send it away for repair (I'd rather spend £25 to buy a replacement drive than go through that hassle!).