My go-to tool for resetting forgotten windows passwords used to be  Offline NT password recovery

It still works fine, but I discovered that the underlying tool that does the resets is available on other distributions including Ubuntu Live CD (after apt-get) and it’s fully baked into my favorite System Rescue CD

That tool is chntpw

Even though the manual page says it’s for Windows NT/2000, so far it works on more modern windows too (local users):

Windows XP
Windows Vista
Windows 7
Windows 8
Windows 8.1
Windows 10