Step 1: Boot your Windows 8 iso in any pendrive

Step 2: Boot into your pc.

Step 3: You can see the installation pop up. Now click ‘repair your computer’ option.

Step 4: Now click troubleshoot option and then click advanced options.

Step 5: Next click Command Prompt option.

Step 6: The commands are

c:
cd windows
cd system32
ren utilman.exe utilman_bak.exe
copy cmd.exe utilman.exe
exit

Step 7: Click continue option.

Step 8: Now scroll the lockscreen.

Step 9: Now click the ease of access button at the bottom left corner.

Step 10: Now type ‘control userpasswords2’ and enter.

Step 11: Now you can see reset password option.

Hope you will understand the above steps. Incase any doubts feel free to ask in comments section.