playback problems on new rig

[fsbee]

Ive just built a media centre Pc and have a nvidia 7600gt running a 43"plasma (dvi to Hdmi),When I use Media Player or VLC to play back clips I get sound but just a black screen, I know im short of something (other than knowledge) what do I need to down load.
Also probably not for this thread but does anybody Know how I make image fit screen better, fine for most things but I have to run at a really low resolution to make task bar and buttons big enough to get at (they are just off edge)

[Krispy Kritter]

A black screen is usually the result of the video overlay settings.

There is also a way to adjust resolution / screen placement, but I can't recall at the moment how to do it.