When forgot your Windows 8 password having no reset disk but you have an available Windows 8 setup disk (installation disk), that’s great. Jut boot your computer from this disk to reset your Windows 8 password.
1. Insert Windows 8 setup disc or flash drive into your computer, then boot from the installation disk.
2. After your computer boots up. Click or tap Next on the Windows Setup window.
3. Click or tap Repair your computer.
4. Select Troubleshoot option. On the next Troubleshoot screen select Advanced options. Then on the Advanced options screen select Command Prompt. Then the command prompt window opens.
5. On the command prompt window, type copy c:\windows\system32\utilman.exe c:\ and hit Enter.
6. Type copy c:\windows\system32\cmd.exe c:\windows\system32\utilman.exe and hit Enter. Type Yes and hit Enter to agree to overwrite the file.
7. Now take out the setup disk, and reboot your computer.
8. When get to the logon screen. Click or tap the Ease of Access icon at the bottom-left corner of the screen. The Command Prompt window immediately opens.
9. Type Net User <Username> <New Password> and hit Enter.
Then you will successfully reset your password to a new one.
10. Now you need to reboot your computer from the Windows 8 setup disk again and similarly open Command Prompt and execute the command copy c:\utilman.exe c:\windows\system32\utilman.exe.
Now everything is ok, exit the Windows 8 setup disk and restart your computer. You can log on with your new password.