You can test easily enough if the problem lies in corruption of your user account or is a problem in windows by temporarily enabling the hidden administrator account.
Open command prompt as administrator.
Type net user administrator /active:yes
Restart and you will see 2 accounts on your login screen. Login to administrator.
Windows will build its desktop. Try setting mono audio and default apps.
Reboot and log back in to Administrator. If the settings held then the problem is with your old account. If they did not hold, there is corruption in the OS.
If the settings did NOT hold, open administrative command prompt and run sfc /scannow. Make note if SFC found and fixed anything. If it did, log into your account and see if it resolved your issues. If your account now works correctly, you can stop here, except for running the last command to disable the hidden administrator account.
However, if your account is still messed up, while logged into your MS account, make a new local account. Be sure to give it administrative privileges.
While in your old account, you can't just move your personal files into the new account without running into ownership problems, but you can copy them to external media. Be sure to use the copy command. Once you've saved everything you need, log into your newly created account. Copy the files into the new account. Once you verify everything is working, Delete your old corrupted account, restart, and then change the new local account you built to a MS account.
Turn off the hidden account from an administrative command prompt net user administrator /active:no
Keep in mind you may have to set up certain apps again.
