What DVD installer? If it is a Mac operating system older than the machine in question, it won't work, or if it is a system specific disc that came with another Mac, it won't work.
P.S. Note, Mac Pro is a desktop machine, MacBook Pro is a notebook. Your signature does not refer to the same machine this forum is for. I can request this thread be moved if you posted to the wrong forum.
10.8 does not come with DVD inst aller, you would have had to create one yourself , and there are tutorials here and there but I don't see one from Apple.
Most often depending on age of Mac, it uses ROM code and begins with net-install loader to pull the OS down and set up is via Recovery Mode. Not DVD.
Plus flash installers are larger than DVD would be.