Re: DVD playback
Have you installed the ubuntu-restricted-extras package? If not that should be your next step. Do that and things will probably work. If you still have trouble you will want to add Medibuntu as a repository, and then install libdvdcss2. If you aren't sure how to do any of this run a search on the forums here, and you will find plenty of tutorials. Good luck.
Hardware: Asus M2N-SLI Deluxe, AMD Athlon 64 6400+, 4 gigs DDR2, nVidia 9600GT, 1.5 TB HD storage
Software: Linux Mint 7 x64, Kernel 2.6.31