Question: how to change another user's password in windows 8.1?
Answer: Bring up the Charms menu by pressing the Windows key + [C] simultaneously (touchscreen users: swipe in from the right side)
Click or touch “Settings”
Click “Change PC settings”
Click “Accounts” from the left-hand menu.
Click “Sign-in options”
Under the “Password” section, click “Add” or “Change”