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.