Following some erroneous manipulations, I end up having 4 user folders in C:\Windows\users in addition to the standard ones (Administrator, Default, Public and Guest). I am using only one account and only one login mail address.
How can I tell which is the valid user folder and can I delete the other ones?
That is weird. I’m assuming you are using Win 8.1?
To figure out which one of the profiles you’re using, right-click on your documents folder (when you’re logged in) and look at the location – make sure you are looking at the local folder, not OneDrive.
I couldn’t tell you what the others are from, perhaps you tried to set up other accounts? Or maybe, your username changed? or you have some profile corruption where the Surface couldn’t login using one profile, so it auto-created another. It’s hard to say.
Does it allow you to look inside of each one of these folders to see what in them?