There are lots of free Windows password crackers available, but we've found that Ophcrack is the most effective. Ophcrack can be run from Windows, Linux or Live CD and it uses rainbow tables to find passwords. The following tutorial explains how to install and boot Ophcrack from a portable USB drive to recover Windows 7 password, in case you forgot the administrator login password.
1. Download Ophcrack
The first thing we will need to do is download the CD image from Ophcrack's official website. Ophcrack Live CD is available in two versions, one for Vista/Windows 7 and one for Windows XP. To crack Windows 7 password, you need to download the Ophcrack Vista/7 Live CD.
2. Burn Ophcrack to USB
After downloading the Ophcrack ISO, burn it to your USB drive using the freeware ISO2Disc. Note that just copy the files directly to your USB drive and it won't work. If you don't have a USB drive, then putting Ophcrack on a CD is your only option.
3. Boot from Ophcrack Live USB
Once you have created a Ophcrack Live USB, you will then need to restart your computer and set your BIOS settings to boot from removable drive first. If you don't know how to do this you can check out this article: How to Set Your Computer to Boot from CD or USB Drive.
When it is booting from the USB drive, Ophcrack will begin loading and eventually present you with four options, graphic mode and text mode. We are going to use graphic mode since it is the simplest option, so highlight "Ophcrack graphic mode - automatic" and press Enter.
4. Recover Windows 7 Password
Once Ophcrack has booted completely, it will locate the user accounts on your Windows 7 system and begin cracking their passwords. The process is automatic - you don't usually need to type or click anything. When the passwords are displayed on screen, write them down. Now just boot back into Windows and you can login with the recovered password!
With the free rainbow tables included in Ophcrack Live CD you will not be able to crack every password, but the paid tables range from $100 to $1000 so you may be better off just resetting your password with WindowsUnlocker.