Here's the explanation:
Your DVD Player is version 4.6 It's from OS X 10.4.x (Tiger), two full generations behind your 10.6.8 system.
That can't work on your newer system.
If you have OS X (not iOS, but that's just a detail
) 10.6.8 (Snow Leopard), then your DVD player should be version 5.4
So, you need the newer version. Check in your Applications folder to see what version is actually there. It's possible that you have an older version somewhere else on your drive, and your Dock might have a link to the older version (which can't work). Do a Find File, or use the Spotlight to search for DVD Player, which may show that you have more than one version installed. Find the version that will work (Version 5.4), and delete any others - you can't use the old ones anyway.
If you only have the old version 4.6, and no others, it's possible that you may have lost track, or simply had a bad install of OS X. You may have other "bad" matchups, if your hard drive has had several OS X updates over the years. Your best choice is to reinstall from the Snow Leopard installer DVD. It is white, with a picture of a Snow Leopard on the label. That will assure that you have all the Snow Leopard stuff, and that it is in the proper folders, etc. Run software update to make sure that all updates have been installed.
Come back with your results.
If you are missing your Snow Leopard installer DVD (or you never had one), that's easy to fix. Just $20, direct from Apple. They still sell it online -
http://www.apple.com/shop/product/MC573Z/A/mac-os-x-106-snow-leopard