I have an old laptop that used to be a backup machine. Yesterday my main working computer was broken and need to use the backup machine. However, I can't remember the login password (seems changed it since upgraded to Windows 10). Any way to unlock the computer without data loss?
Without a recovery disk, do you have another account that can log in that computer ? (computer in a domain?)
Usually their is the standard admin account, and the user account used on the computer.
You can also use the HDD from another computer to make a backup, and re-install it in the correct computer, and re-install Windows on it.
If you think this is a trouble, try some free windows password reset tools like ntpassword, uukeys, ophrack and more...
you should prepare an USB or DVD and a working computer to burn a password reset disk.