If you forgot your administrator password on Windows NT/2000/XP/2003 you have two chances: a cumbersome recover process and use some third non-free party tools or use Ophcrack, a nice (open-source) password recovering tool. It comes even on a LiveCD if you totally lost access to your computer.
Ophcrack is a Windows password cracker based on rainbow tables. It is a very efficient implementation of rainbow tables done by the inventors of the method. It comes with a GTK+ Graphical User Interface and runs on Windows, Mac OS X (Intel CPU) as well as on Linux. You can use it to recover passwords up to 14 characters long. Features:
- Runs on Windows, Linux and Mac OS X (intel).
- Cracks LM and NTLM hashes.
- Free tables available for alphanumeric LM hashes.
- Loads hashes from local SAM, remote SAM.
- Loads hashes from encrypted SAM recovered from a Windows partition.