Hiren's boot bootable ISO contain a few tools that can reactivate and delete the password for windows accounts (so can be used on the builtin administrator account) - afterwards, you just need to restart, log in the administrator account, then you can reset other local accounts passwords from there.

Of course : it will not work on MS accounts, and it will not work on bitlocked drives (unless you have the bitlocker key / recovery key)

As others said, only do that with the explicit consent of the person who used the account.

If you just bought a third party computer that was not reset beforehand, you can simply reinstall windows (windows 10+ computers with valid license keys are registered on microsoft servers, and should reactivate automatically after full wipe & reinstall of the same version of windows (if it's reinstalled on the original hardware it was installed on)