Great !
The first phase (the replacement of the 2 files with the ones from WinXP) worked greatly.
But in this way I lost the bookmarks already accumulated in Win10 (however I preserved those replaced files).
Using the Opera browser function "export bookmarks" created an .html file of the bookmarks in Win10, .html file that
enabled me to import/recover the Win10 bookmarks.
Many thanks again.
