1. Boot from the Windows 10 DVD/USB. Make sure that your PC setup is configured to boot from a DVD and that UEFI and Secure Boot are disabled.
2. Press SHIFT + F10 to open a command prompt.
3. Replace the file utilman.exe with cmd.exe. Before you do this, you should make a copy of utilman.exe so that you can restore it later. Note that you can only restore this file if you boot again from the Windows DVD. Windows 10 is usually installed on drive D: if you boot from a DVD. You can verify this with "dir d:\windows\system32\utilman.exe." If the system can't find utilman.exe, try other drive letters.
move d:\windows\system32\utilman.exe d:\windows\system32\utilman.exe.bak
copy d:\windows\system32\cmd.exe d:\windows\system32\utilman.exe
4. After you have replaced utilman.exe successfully, you can remove the DVD and restart your problematic Windows 10 installation.
wpeutil reboot
5. On the Windows 10 sign-in page, click the Utility Manager icon.
6. You can now add a new user with the command below. We also have to add the user to the administrator group so that we regain full control of our Windows installation. Replace <username> with the account name of your choice. Note that the account name must not exist on this Windows installation. Don’t let the Windows 10 screen saver distract you.
net user <username> /add
net localgroup administrators <username> /add
7. Click the screen to make the sign-in page appear again. Your new account should show up, and you can sign in without a password.