But what should you do to fix the problem when you have deleted an administrator account on Windows 10 by mistake? //

1. Click on the Start button to open Start menu.
2. Press the Shift key and hold it.
3. Choose Restart from the Start menu.
4. Wait for the rebooting until you enter the Windows Recovery Environment.
5. Choose Troubleshoot and Advanced Options to see the window shown below.
6. Select Command Prompt and repeat step 4 ~ 8.
7. Type net user administrator /active: yes and hit Enter.
8. Wait for it to complete.
9. Type net localgroup administrators UserName /add (please replace UserName with your current account name) and hit Enter.
10. Create a new user account with administrator rights.
11. Type net user username * /add