windows 10 flushed ALL personalization settings

so, got a british buddy whose windows 10 computer has seen fit to flush ALL personalized settings..I'm talking from screensaver, to wallpaper, even his google chrome is looking factory install fresh if you catch my drift.

to say he is NOT a happy camper is like saying it rains in monsoon season.

now I've never heard of an os just flushing the settings like that, so here I am, to ask a question.

my question is rather simple..what possible occurrences could have seen this happen? and how does he stop it happening again?

Hi ... Did he by chance switch account from a Microsoft to local ?

he apparently inadvertently signed into a temp account, dont ask me how that happened.

It sounds like he may have gotten a user profile error that led to the temp account.

If so, the tutorial below matching the exact error should help.

You've been signed in with a temporary profile - Fix

User Profile Service failed the sign-in - Fix in Windows 8