There is so little substance to the description of what software has been used, what processes have been run, what data has been input/out from/to where. You quote your friend as "thinks some of the data may be created within the apps' folders." but seem unsure about that. There is so little for anyone to go on that neither Microsoft or anyone else has even a remote chance of knowing where to begin. You might statrt by listing the "non-Microsoft apps" which have been run, using what data and with what objectives.Microsoft need to get a grip of such a situation and offer/create a repair that works. I have Win10 on a memory stick.
Anny hope of a solution out there?
LesM