My concern was particularly about what settings would get changed (as I've set a number of custom settings).
In case anyone else has issues.....
So I ran WMP .....on the WMP Welcome screen I selected Custom Settings.
Then on Privacy Options just accepted what was presented (it was as I had set-up previously).
Then on Select Default Music & Video Player I selected Choose File Types and then Finish. A File Associations window for WMP opened but all was as I wanted.
Then launched WMP and settings all seemed to be as I wanted.
Maybe on the Welcome screen I might have been able to select to let WMP set its defaults and it might have carried over my previous settings. Who knows. But I'm back where I was before now. That's all I'm concerned with.
Only other wrinkle was that I restored the Quick Launch WMP shortcut before running through the Welcome Screen and this removed the Quick Launch shortcut again (on both machines). So reinstated again and seems to have stuck now.