Ok, I just connected my pc to my home theater system. It displays everything thats on my computer monitor on the tv fine (Games etc.). But It will not play videos from the computer (Dvd's, Avi's), It just shows up as black. It does however play movies from the internet, like video clips and everything. Just not full length movies (Dvd's Avi's).
What are you using to play them with? WMP sucks at this. Try WinDVD, or PowerDVD, and look for the setting to display on TV.
Did you adjust your graphics options when you configured your tv-out option so it is designated as either ntsc or pal? I had the same problem before and I believe that is all I had to do.
its set to pal, ive tried using wmp, and divx. I can see everything else fine on the tv except for videos, avi and dvd's for example.