If you have forgotten your administrator password or any local account password on your machine, follow these quick steps to regain access to your machine. This process also works for Vista and Windows 7.
The only thing required is a CD/DVD/USB of your Windows Vista/7/8 ISO.
Start your computer with the above USB/DVD attached and ensure you press a key when prompted “Press any key to boot from CD or DVD” :
Once your ISO has booted up (here I am using a Windows 7 ISO), click on Next :
Then click on “Repair your computer”: