Change administrator password on windows 7 with autologon without knowing the old one

Question

I have a Windows 7 machine that is set up with automatic logon. It is an internal machine not reachable by anything so security isn't an issue.

I don't remember what the password is, but in order to install some some software that will run as a service I need to input the current password.

The question is, how can I change the password on the administrator account without knowing the current password? Note that since it is set up with automatic logon, I have full access to the machine, but both Ctrl+Alt+Del change password and the control panel user manager change password requires the old password before changing.

Is this possible?

Answer 1

The automatic logon stores the password in the registry as plain text.

It is located here: HKLM\Software\Microsoft\Windows NT\CurrentVersion\winlogon There's a key called DefaultPassword.

Alternatively, you could create a new account with administrator rights, login with that, and use it to change the first one's password.

Answer 2

Simply read out the old password. As long as AutoLogon works and you are logged in with the AutoLogon User you can reveal the password: https://superuser.com/a/1780884/898594

Answer 3

Yes, it is possible. There are at least three ways to do this:

1. Change the password with an other administrator account.
   This assumes that you have such an account.
2. Reset the password by booting from a liveCD.
3. Move the harddisk with windows to another computer and replace sethc.exe

More details on that here (works for not just XP).