Step 1: Create a bootable usb or CD.
Step 2: First, start by booting your Windows 10 installation into the setup by changing the boot order in your BIOS to take priority with the CD.
step 3: click on repair computer and select advanced options.
step 4: click on command prompt.
Step 5: use below commands
move d:\windows\system32\utilman.exe d:\windows\system32\utilman.exe.bak
copy d:\windows\system32\cmd.exe d:\windows\system32\utilman.exe
step 6: if it is not working change the directory to c:
step 7: Once this is complete, use the command “wpeutil reboot” to restart the machine.
step 8:After you’re back at the login screen, click the Utility Manager. If everything went right, you should see a cmd.exe launch.
step 9: Type ” Net users “ command.
step 10: net user <username> <password>
step 11: Exit and login with new password
Change password in Computer Management
Step 1: Log on to Windows 10 as administrator.
Step 2: Open the Computer Management. (Press Win + X and select Computer Management.)
Step 3: Expand the “Local User and Groups” folder and click “Users” folder.
Step 4: Right click on the password forgotten local user account. And click Set Password.
By this way you can reset your Windows 8.1 password to a new one but you will lose some data in this local user account.
Reset password with Command Prompt
Similarly, log on to Windows 8.1 as admin. Press Win + X and select Command Prompt (Admin) to bring out Command Prompt window. On the Window, run the command net user <Username> <New Password>.
When it displays The command completed successfully you have reset your Windows 8.1 user login password to a new one. For example, I have reset the password for account Ting to abc.
Warning: Following these steps will remove all of your data, programs, and settings.
Start your PC and select the Power icon in the bottom right-hand corner of the lock screen.
While holding down the Shift key, select Restart.
On the Boot options menu, select Troubleshoot > Reset this PC > Remove everything.
Your PC will restart and will reset itself.