Thanks Everybody for your answers.

I'm sorry but really don't remember the way i have installed it. (it was a looong time ago)

I will try to flash it (Have tryed installing "flasher-3.5.exe" on Windows 10. Clicking on the .exe, the program's window opens and shuts down after a millisecond... is it the way it works?) and i'm totally newbie with command manip!

Question : Is it possible to flash the device even if it stays quite after having connected it with a PC.
I only see the screen with this beautiful gray dark nokia watermark appearing after the "bzz"...

Thanks for your help