To simply put, the main objective is to be able to access the command prompt. The ability to do this is most simply renaming cmd.exe in Windows/System32 folder to a file that is able to be launched on the login screen.

Utilman.exe is the most common one for Windows Vista. You can either use a Live CD, such as Hiren’s BootCD or a Windows 7 installation USB, using the repair option access either Command Prompt or a file explorer (via driver options) to then do the rename process, located in Windows/System32 folder.

Utilman is the bottom left corner icon that would display the accessibility options on the login screen. Renaming cmd.exe to Utilman.exe basically means when you go to turn on this option, the command prompt opens instead.

Steps

Step 1 (to list all users): Net User
Step 2 (to trigger password change): Net User <username> *

Download | Hiren’s BootCD PE
https://www.hirensbootcd.org/download/

How to reset password on Windows 7/ Vista / XP – YouTube
https://www.youtube.com/watch?v=dBf2iqmx5ns

A last resort would be to access the drive via another system and rename the files that way.

Net user | Microsoft Learn
https://learn.microsoft.com/en-us/previous-versions/windows/it-pro/windows-server-2012-r2-and-2012/cc771865(v=ws.11)

Net User Command (Examples, Options, Switches, & More)
https://www.lifewire.com/net-user-command-2618097