So it works when not using "easy install" as André explained earlier.
Thanks dlhotka to point to a solution and a.p. to explain it. Even if I did dozen of tests, it's likely that I would not have thinked to this without your kind help.
One more optional question if you please, I noticed that when installing W7 like that, my new VM got automatically some drivers from the hardware machine (at least ethernet,usb). I was surprised as I expected to install them as I was using an original cd. Can you explain ? Why ethernet, usb and not display ?