Got it !
the problem comes from the USB management on VirtualBox; for anyone facing this kind of problem, I would recommend this link: https://doc.ubuntu-fr.org/virtualbox
After the installation of the extension package, you have to activate USB2 in the parameters of VirtualBox.
Launch XP, then USB available devices appear with a right clic on the usb icon on the VBox machine, under the WinXP window... You just have to select the Velleman ...
So at the end of the day, the oscilloscope can run !!