You can use WinPassword to reset the password to a known one.
For that purpose, you will need the access to the registry files SYSTEM and SAM.
These files are stored in the folder
Windows\System32\Config. When Windows is loaded, it disallows accessing these
files. Please follow these recommended instructions to reset the password.
1. First, we will need to obtain the files SYSTEM and SAM from the system,
password to which we are about to reset. To achieve that, we will need to load
another copy of Windows on the computer that normally runs the copy of Windows
that you need to reset password for. If there are two different copies of
Windows installed on the computer, you can load the second copy. If the computer
has just a single edition of Windows, you will need to use a boot CD-ROM disk.
You can create a boot CD, for example, using the third-party software named Bart
PE http://www.nu2.nu/pebuilder/
(it's free). Now boot the computer from the system disk and then copy the
files SYSTEM and SAM from the folder Windows\System32\Config to a USB flash
disk.
2. On another computer, which has WinPassword installed and running, reset the
password using the menu command Tools | Reset Password. You will need to specify
path to the files SYSTEM and SAM, which you copied during the previous step.
WinPassword will ask you to select the user whose password is to be reset.
Normally, it makes sense to reset Administrator's password. WinPassword will
change the selected user's password to "abc" and create a backup copy of the
file SAM, saved as SAM backup. In case of the necessity, you can restore the
system's original state.
3. Copy the modified file SAM back (the file SYSTEM is used for resetting
password; however, it remains intact).
The reset password feature is available in the Pro edition only.
The upcoming edition of WinPassword will implement a more convenient automatic
password reset with a boot disk.