Touch or click on Troubleshoot, then Advanced options, and finally Command Prompt.
Now that Command Prompt is open, type the following command:
copy c:\windows\system32\utilman.exe c:\
…and then press Enter. You should see a 1 file(s) copied confirmation.
Next, type this command, again followed by Enter:
copy c:\windows\system32\cmd.exe c:\windows\system32\utilman.exe
Answer with Y or Yes to question about the overwrite of the utilman.exe file. You should now see another file copy confirmation.
Remove any flash drives or discs that you may have booted from in Step 1 and then restart your computer.
Once the Windows 8 logon screen is available, click the Ease of Access icon at the bottom-left corner of the screen. Command Prompt should now open.
Next you need to execute the net user command as shown below, replacing myusername with your user name, and mynewpassword with the password you’d like to begin using:
net user myusername mynewpassword
For example, on my computer, I would execute the command like this:
net user "Tim Fisher" a@rdvarksar3skarY
Note: You only need to use double quotes around your username if it happens to have a space in it.