I have a Lenovo think pad with Ubuntu 14.04 installed I set a new password to the administrator account and I forget what that is. I can use the machine but making changes it asks for the password in which I forgot it. Is their a back door or a way to change it?
The password that you set-up on installation process is the password of your account, not the administrator account.
In normal cases, you can change your password using
passwd, but since you forgot the password for your account, so you need to log in as the root account.
Follow above link and do processes. When you change password, put
passwd *youraccount* command.