OK, I gave up.....
Spent two hours, cleaning up the registry both by hand and with ccleaner, looking for hidden folders, resetting win10 to a previous state. Nothing changed. Gameex AE is still messed up, failing to detect the games, failing to load my settings, failing to save them properly from the wizard.
since I don't have an exorcist handy, nor presently the time to resintall win10 from scratch, I've installed Gameex standard edition and while it is still picking up some unwanted information it shouldn't be aware of (eg: my emumovies account details), after some cursing as only Italians can, and some hand-editing of the config files, at least it works. It would have been easier id the config flle was somehow ordered and not with all settings randomized through the file, but OK, I did it. I'll feed my kids this now. If they mess this up too, I'll have to change frontend...