Hi, Ztruker
I will be pleased to receive your further and complementary suggestions for solving my problem.
As you are aware my HP laptop only have installed KB 3105213 and 3116869, so upgrade version 1511 and subsequent updates are missing and i can neither install them manually by myself nor by means of Windows Update.

Using the various ISO that I downloaded from Microsoft sites, installation starts normally but it continue to stuck at 25%, my nightmare.
Do you have additional ideas on how to solve this problem? I thought that W10 was the cream of the cream OS, however...
By the moment I only can use Windows Update for updates to Windows Defender.

Many thanks in advance.