I have a mini-DVI to DSub cable and an audio cable connecting my Macbook to my Samsung LCD HD TV. I get the audio portion from the computer to the TV fine, but the only video is the computer desktop background. Any suggestions will be appreciated.
That is because you have an extended desktop. Take a look at System Preferences > Displays > Arrangement to see where the extended desktop is located, normally it is on the right. You can also use MIRROR DISPLAYS, but that will limit the TV's resolution to 1280 x 800, except if the TV is not an HD TV, then the MacBook's resolution will be lowered to the TV's resolution.
There is no Arrangement option visible while you have the TV connected to your Mac via adapter and are able to see your background image on the external TV?
What does happen, if you move a window to the top, bottom, left or right? Does it become partially visible on the TV?
Btw, that Arrangement option should be there, as you obviously have Mac OS X 10.5.x Leopard, and the screenshots I provided are from Mac OS X 10.2.