Is it CD's or DVD's specifically? Are they commercial movies, for example?
I can't exactly help with music CD's other than suggest you search for 'codecs' but for commercial movies, you likely need 'libdvdcss' which is a DVD movie de-cryption library required to play most DVD's.
Using Google, you can very easily locate a libdvdcss package to download and install. It's quick and simple, and should solve the DVD issue if this is infact the problem.
Let me know how you make out, or if you need further help