If you forgot the admin password and have no other account with administrator rights, things can get tricky. The methods and free tools explained here can reset the Windows password for all Windows versions. As system administrator, you are usually confronted with this problem if users have admin rights on their machines. Even if you don't have to reset a password now, you should get acquainted with this issue. Rest assured that sooner or later a user will bug you with this problem. I must admit that I managed to forget my password more than once.
Use your password reset disk to recover the Windows password
Windows 10/8/7 allow you to create a password reset disk, which enables you to reset your password without much hassle. The problem with this option is that you have to create the reset disk before the password is lost. Thus if you don't have a password reset disk, this option is not for you.
Reset Windows administrator password with the Sticky Keys trick
The Sticky Keys trick to restore a forgotten administrator password is a reliable way to reset a Windows 7 administrator password , and does not require third-party software. All you have to do is boot up from a Windows 7 or Windows Vista setup DVD, launch the Windows Recovery Environment (RE), and then replace the sethc.exe file with cmd.exe. You can also use this method for Windows XP, but you have to use a Windows 8 or Windows 7 DVD.