No problem, once installed ....

I take a star for the lack of relevant information about the installation process.
On a machine with UEFI BIOS with multiple operating systems, the most convenient is to install Windows 7 on a blank disc; because already organized on a disk in Gpt and therefore already includes the ESP, W7 recreates a new ESP partition surcharge, which indicates a broad confusion!
By cons, on a blank disk, Windows 7 creates the partitionement in Gpt and the ESP and MSR partitions before settling in a third partition. Note that the partitionement Gpt created GPTUID fully respects the standard and thus permits installation on other OS partitions later