Error playing .mov file ?

Hello,

I am getting the following message when trying to play a .mov file with QuickTime Player.

"QuickTime Player can't open "FG demo by Roy.MOV" because the movie's file format isn't recognized."

Is there a reason why this is happening? I thought QTP supported such files. How can I fix this problem, I need to open this .mov file it's important.

Thanks

Edwin