:sl:
It would be usefull if you had given us some details regarding your computer.
First I will assume that you have a dvd drive in your system but you want to view DVD video on it right ? If its not displaying the video when the DVD is inserted its likely a Codec problem, I advice you to download and install the K-lite Mega Codec pack which is available on this site
http://home.hccnet.nl/h.edskes/mirror.htm there should be about 5 similar links, grab the download from any of them.
If you are unsure about your system look for any signs that say "DVD" such as on the cd drives as illustrated below