This article shows you how to reset a windows password.
Boot up your PC from you linux partition or an usb stick. Then you replace the Utilman.exe with cmd.exe in C:\Windows\System32 as shown below:
cd /<mount_point>/Windows/System32 cp Utilman.exe Utilman.exe.orig cp cmd.exe Utilman.exe
Now boot up your Windows and click on the accessibility tools icon or press WIN+U. This will open an administrator command prompt for you. With this prompt you are able to create new users or enable the administrator account.