You can boot with Windows installation DVD, access the Command Prompt and replace sethc.exe with cmd.exe. Reboot to the login screen and press SHIFT key 5 times and the command prompt will launch. Run the "net user" command to reset your password or create a new admin user:
https://www.howtogeek.com/96630/how-...-the-easy-way/
https://www.top-password.com/knowled...eset-disk.html

Or use the third party password cracking tools:
http://ophcrack.sourceforge.net/
https://www.lifewire.com/free-window...-tools-2626179