Step 1)
Insert the installation disk to your locked computer, restart. When following installation appears. Click on “Repair your computer”.
Step 2)
Click on command prompt
Step3)
When a Command Prompt black screen appears, type
"copy c:\windows\system32\sethc.exe" and press Enter. Then type
"copy c:\windows\system32\cmd.exe c:\windows\system32\sethc.exe" afterwards press Enter key
Here what happens is the .exe file which is dedicated to trigger when we press shift key 5 times going to replace with cmd.exe. So when we press 5 times at the login window cmd will be appear.
Step4)
Restart your computer. On the login screen, tap Shift key five times and you'll see a command prompt screen in administrator mode
type "net user UserName NewPassword"
(replace the UserName and UserPassword with the one you need) and press Enter key.
The user password will be replaced with new one. Close the window and then you can log in that user with new password.
Note: This will only work for local accounts