Reset Local Admin Password on Windows 7 machine

Are you able to access the computer remotely using psexec (from sysinternals)?

psexec /s \\windows7_workstation cmd
The other option is to use a GPO to setup a local administrator account using a startup script?

Is this what might have happened?
https://www.experts-exchange.com/questions/26519246/The-trust-relationship-between-this-workstation-and-the-primary-domain-failed-Windows-7.html

I answered this question:
https://www.experts-exchange.com/questions/27187903/Forgot-my-password-on-Windows-7.html

Please try removing the network cable/disable wireless and login as domain admin
or login as any user which is logged in before as admin

In my experience, the easiest and most reliable method is using the disc that Moomin83 recommended in the very first reply.

After you have burned that ISO to disc, boot up into the Linux environment and reset your password.  I have been using this utility to help people with their forgotten Windows passwords for over ten years, and unless the hard drive has actually been encrypted it has worked every time! Here is a comprehensive tutorial on how to utilize it:

http://pcsupport.about.com/od/toolsofthetrade/ss/ontpre-screenshot-guide.htm

http://pcsupport.about.com/od/toolsofthetrade/ss/ontpre-screenshot-guide-p2.htm

There are two important steps within that tutorial that warrant extra attention:

- When you reach the User Edit Menu stage of the process it's best to select "1" to Clear (blank) user password.  You can always change the password to something more secure after you successfully log into Windows with the blank password.

- When you reach Step FOUR: Writing back changes, you will be queried with About to write file(s) back! Do it? [n].  If you inadvertently pressed Enter on this screen the changes won’t go into effect.  You need to specifically type "y" first for the updates to be written to the operating system.

this works, thanks