When forgot domain password, we may try our best to change domain password. While, the fact is that Windows domain password change is far more complicated than your local Windows password change.

Before you forgot the domain admin password
In this situation, to change the domain password is quite similar to what a local Windows password does. As for the specific differences, please see the below.

Method1: Using CTRL+ALT+DEL to change Windows domain password
This is the easiest one as far as I am concerned.

1. On your computer desktop, press CTRL+ALT+DEL.
2. In the Windows Security screen, click “Change Password”.
3. In the User name box, enter your login name.
4. In the password box enter your old password and new password respectively, and then click “OK” to finish.

(Note: Your new password should contain at least 3 of the following elements: English uppercase characters; English lowercase characters; Base 10 digits; Non-alphabetic characters.)

Method2: Change domain administrator password by using command prompt

1. Click “Start” and then go to “Run”, next enter “cmd”.
2. Now the command prompt has opened, using the following commands to change domain password: net user Happy Re123456. (Note: Happy is your domain username, and Re123456 is the new password, also this password should meet certain requirements which have been discussed in Method1.)
3. Press “Enter” to finish the change.

However, the complex thing is the situation that you forgot the Windows domain password. So the methods above cannot be useful any more. Then, new ways should be figured out.

When you forgot domain password
Method3: Change domain admin password and other domain passwords with Windows Password Recovery Ultimate

Step1. Download Windows Password Recovery Ultimate online by searching for it on any search engine.
Step2.: Install the program to any unlocked computer, and prepare for a blank CD/DVD or USB Flash Drive.
Step3. Insert the prepared CD/DVD/USB to computer for burning the Windows Password Recovery Ultimate ISO image file into it. This can be easily done by clicking “Burn” button in the interface of that program.
Step4. After the burning process finishes, you just take out of your newly burned device and insert it to your locked computer.
Step5. Start the locked computer and set it boot from CD/DVD/USB Flash Drive. After setting done, reboot the computer.
Step6. Change domain password simply by clicking “Reset your password” icon in the interface after computer restarted.

Note: by using Windows Password Recovery Ultimate to change domain password, the newly password doesn’t have the need to meet the domain password policy in Method1. But here, my suggestion is that you’d better make your domain password strong for the sake of security.

Source: http://www.windowspasswordrecovery.net/article/change-domain-password.html