To reset Windows 7 or windows Vista password please follow the below steps:

•    Set the Boot Priority in the BIOS of your systems to boot first from the optical drive and then insert your windows installation disk and restart your system.

•    On the first screen that appears, select the language you are comfortable in and then on the next screen select "Repair Your Computer" option.

•    Finally you should arrive at System Recovery screen where you need to select the first option i.e. recovery tools and highlight the drive letter where the Windows system is installed and click on Next.

•    Under the next screen select the command prompt option and enter "regedit" (without quotes) in the command prompt. This will open the registry editor.

•    In the Registry editor window, navigate to HKEY_LOCAL_MACHINE, click on File and then on load hive.

•    In the load hive dialog box, navigate to the <%windir>\system\config\folder and select the SYSTEM file.

•    This will bring up the load hive name box, where you need to enter some name. It can be anything really, it doesn’t matter.

•    Then expand the newly loaded hive and select "setup" under the hive.

•    On the details pane, select the "SetupType" option and modify it. Under the ValueData enter the value 2 and click on OK.

•    In the details pane again, select CmdLine and modify it to enter cmd.exe in ValueDate.

•    Now close the registry by clicking on File menu and exit.

•    Open the registry again by using the regedit.exe command in the command prompt.

•    On the left under the HKEY_LOCAL_MACHINE click on the hive that you loaded earlier and then click on upload hive.

•    Click on Yes if prompted.

•    Close the command prompt and click on Restart on the system recovery option window.

•    When the system restarts, there will be a command prompt.
Enter net user <username> <new password>. So if your username was john, enter net user john xyz123 (Where xyz123 is the new password).