Thsi is a guide to reset your local windows password.
⚠️ If you dont exactly understand what you do here, this could break your operating system. Please be carefull!
Boot from another live operating system, for example from a USB stick with Linux or something similar (e.g. http://www.knoppix.org/). You need a console where you can access the hard disk of the computer.
You can also use the Windows installation CD. You can open the command line in the installation screen with SHIFT
+ F10