Question : How could I display the file extensions in the file explorer of windows mobile 6 ?

All is said.
Thanks for your help.

Answer : How could I display the file extensions in the file explorer of windows mobile 6 ?

I don't believe this can be done natively

There are a few 3rd party products that can be used though such as:
Total Commander: http://www.ghisler.com/ce.htm
Resco File Explorer: http://www.resco.net/pocketpc/explorer/default.asp