Here is an annoying thing

[Jozsef Mak]

When i double click a video clip to play it in Mplayer a window pops up with 
the following message;

The filename "ogy.wmv" indicates that this file is of type "Microsoft WMV 
video". The contents of the file indicate that the file is of type 
"Microsoft ASF video". If you open this file, the file might present a 
security risk to your system.

Do not open the file unless you created the file yourself, or received the 
file from a trusted source. To open the file, rename the file to the correct 
extension for "Microsoft ASF video", then open the file normally. 
Alternatively, use the Open With menu to choose a specific application for 
the file.

Then i have to rename the file each time otherwise the system doesn't let me 
play.

I am not sure that this message is generated by Ubuntu or Mplayer. What i 
know is that extremely annoying. How can i make this thing go away?

jozsefmak