I faced a problem with a lost of password for a windows PC. Here what I did

1. Download ISO for bootable Offline Windows Password here. Scroll down to download section and download cd140201.zip regardless you want to build CD or USB boot
2. Crete a bootable USB with rufus
3. Boot using the USB thumb drive and just go through the questions. You can reset and enable any user account.

Credit to about.com for the info