Windows 10 reset itself (and deleted my profile & documents)

[chalky]

I went to run my Windows 10 (1909) PC this morning. During startup, it tried to load my profile before displaying an error (User Login Service not started). A message appeared saying I could not be logged in, followed by an empty screen with a "STOP" button in the centre. Having no other option, I clicked the button, and the PC restarted.

When restarting it got beyond the login stage, but displayed "Preparing Windows" for almost 20 minutes - at the end of which the desktop loaded. I was pretty alarmed to see no pinned taskbar icons, or usual window wallpaper. Instead I had default wallpaper, and taskbar icons for Edge, Mail, Explorer (and something else) with associated desktop shortcuts. Confused, I tried running a few programs (all of which still seemed to be installed) and every one of them acted as though it was the first time I had run them (they've been installed for at least 2 years). Firefox and Thunderbird were both using default profiles, with none of my bookmarks or email accounts to be seen.

For some reason, during the restart, Windows had created a 'temporary' user and logged me in using it without telling me. Ok - no problem - presumably all I needed to do was log out and log in again using my 'real' profile? Sadly not - as Windows simply booted into the same state, although this time I was logged in on my profile rather than a temporary one. However, when I went to my documents folder, it was empty. Further investigation revealed that ALL the contents of "My Documents" (plus the "Pictures" & "Music" libraries) had been deleted. Even stranger, 2 applications of my own which were installed in folder "C:/Applications" had also been removed - yet those which weren't mine remained.

I have just spent the whole day trying to restore my documents etc. from a backup, but Windows is now running like a dog and many applications are crashing due to missing/corrupt installations - particularly Cubase & Wavelab, both of whom complain about plugins and missing sample libraries - and I am running out of ideas on what I can do other than a complete reinstall of everything (which will take another couple of days). This has totally destroyed my faith in the OS - I rely on my PC to make a living (it is the heart of my recording studio) and will have lost several days work through no fault of my own by the time it is sorted.

As soon as I am able to I will export all my projects to my 8-year old iMac as my business simply cannot accommodate this kind of outage. I'm not an Apple (or Logic Pro) fan, but their OS has NEVER caused issues like this one.

I have searched the internet for other similar reports, but have found none. Has anyone heard of this happening to anyone else - and if so, is there a known reason or workaround to prevent it happening again?

[Amon]

I have honestly never heard of this happening before.

Do you have security software; has your system been compromised by malware etc. Honestly I do not know why this happened and again I have never heard of this happening before.

[Kryzon]

Is there a way for you to check disk health (CHKDSK comes to mind)? It could be a hardware problem.

[col]

Number 1 rule of today is NEVER trust a Microsoft update to go smoothly.

Your initial issue is a very well known issue - getting logged into a temporary account...

For some reason, during the restart, Windows had created a 'temporary' user and logged me in using it without telling me

Yeah you would have that you own the OS but no you don't and you've given Microsoft the legal right to do whatever they want with it regardless of what you may be thinking.
The temporary account is an admin account used for 'updating' the OS. The update process could get all confused because... well who knows why nowadays - even Microsoft don't know half the time.

I rely on my PC to make a living (it is the heart of my recording studio) and will have lost several days work through no fault of my own by the time it is sorted.

Welcome to the new era of Windows10 that thousands of folks insist doesn't exists, although clearly and 100% it does. You could try reach out to Microsoft but to save you from further frustration and wasted time in phone calls... they really don't care about your individual circumstance or situation. Sad but true.

I've also heard of this dilemma of getting into your account and everything is gone. Some people say that they've logged into 'safe mode' and rebooted the PC and everything has come back as if nothing had happened and the update had gone well. Or you could try a 'rollback' to a previous version - if it works then back up your latest version before it wants to break your PC by reinstalling the update again.

Quick google search and maybe this huge thread could help resolve your issue?
https://www.tenforums.com/tutorials/48012-fix-youve-been-signed-temporary-profile-windows-10-a.html