Media Player video size problems

When I try to play video with Media Player I don't get the full
picture. Only a square from the middle of the video is shown, so for
example, I get torsos, with no heads and no legs instead of the full
picture of a group of people.

When I run the video out to a TV, everything is fine on the TV, and
still messed up on the computer. The videos also display properly on
other computers.

I have tried uninstalling, reinstalling, upgrading, etc and have the
same problems in Media Player 9, 10, and 11.

Any ideas?