It's a well known exploit on Windows:

• delete sethc.exe (sticky keys executable) from the system32 directory.
• replace it with a copy of cmd.exe (name it sethc.exe)
• reboot to login screen.
• shift 5 times, and you get a command prompt with administrator privileges

Now, you can change all the passwords on the system from the login screen.

Last I checked, it still works, and it's been around since xp days.