unknown user

Has anyone other than your daughter or another close family member had access to the pc? If you don't receive a list of users then the main/primary account has been either changed by someone or you've possibly been hacked & the account changed remotely.
Try & access the built in administrator account.

1. Click/Tap on the Power button under the Start Menu or on the lower right-hand side of the Login screen, press and hold the Shift key, and click/tap on Restart. This will open a command prompt at boot.

Then type:

net user Administrator /active:yes

If for some reason that doesn't work, do the following:

1. In the command prompt, type regedit, and press Enter.
   
2. In the left pane of Registry Editor, click/tap on the HKEY_LOCAL_MACHINE key.
   
3. Click/tap on File (menu bar), and on Load Hive.
4. Open the drive (ex: D ) that you have Windows 10 installed on, and browse to the location below. NOTE: The drive letter (ex: C) will not always be the same at boot as it is from within Windows 10.
   D:\Windows\System32\config
   
5. Select the SAM file, and click/tap on Open.
6. In the Load Hive dialog, type REM_SAM, and click/tap on OK.
7. In the left pane of Registry Editor, navigate to and open the key: HKEY_LOCAL_MACHINE\REM_SAM\SAM\Domains\Accounts\Users\000001F4
8. In the right pane of the 000001F4 key, double click/tap on the F binary value to modify it.
9. In line 0038, change 11 to 10, click/tap on OK.
10. Close Registry Editor and the command prompt.
11. Click/tap on Continue to startup back in Windows 10.

NOTE: To disable the Administrator account simply reverse Step 10.

The see if you can edit/ fix the problem account or create a new one. Once in I'd first backup any important data in case you need to reinstall Windows to fix.
HTH,

gregrobbins said:

There is nothing to press. I start the computer and this screen comes up.

The start icon is on the lower right hand side of the screen you posted, the circle with the vertical line through the top.