If you forget your old password or any other reason and want to change your administrator password then follow these steps
Go to Control Panel >> Administrative tools >> Computer management >> Then System
Tools
After That Go to Local user and Groups >> User
Then on Administrator Do Right Click and then Set Password >> Then Click Proceed
Now enter your new password and press ok button.
Go to Control Panel >> Administrative tools >> Computer management >> Then System
After That Go to Local user and Groups >> User
Then on Administrator Do Right Click and then Set Password >> Then Click Proceed
Now enter your new password and press ok button.
I hope it is helpful for you to solve your problem.