Picture not coming up?

For some reson when I try and play any movie or video file in any player the sound works but no picture comes up, I have no idea why this has happend.

Any help? Thanks

has video ever come up? its probably some missing codec.

Yes every day for the last 3 years untill now.

Have you installed or downloaded anything new? Put any cd/dvd’s in your drive that may have had Sony Arcos on them? Updated any drivers?