The problem is solved !
I was (am still) having trouble with my memory module and it didn't work at natural frequency (2400MHz, I had to downgrade it to 2133...) then it prevented Windows 64bits to start and install... On the multiple trials and restarts, Windows (?) seems to switched the install into the 32bits version because this version was finally installed and I haven't noticed that ;-( (I have the both on the USB disk).
(I resinstalled everything in 64 bits and it's ok except the memory)
thanks for helping
MODERATOR NOTE: I am glad to see you have resolved your issue. To help keep this post on topic and help other with a similar issue, I am locking this thread.