On the base of our exchange, I have now made a "proper" installation of BiaB 2019 on my new computer.
I have set it to the location where BiaB already was (my internal hard disk)since I have not enough room for the complete program under C/ and it works! I have now been able to install the update 633. I suppose that, by a proper installation, some registrations files are set into the computer...
Thanks for all good advices, it is good to be helped when nothing works!
Carca