Locked out of Administrator, "file does not have a program associated"

I was attempting to change the User administrator name so that it reflected a new windows explorer file path. When my SO set up the machine, she set the user name as "Mike & Steph". Well, this is now in the file path for all of our files and I work with software where no special characters or spaces can be in the file path.


As I tried to change it, I found a forum that said to create a new local user, set it as the administrator, and delete the old one. I was wary of deleting the old one, so I created a new local user, made it the Administrator, then restarted the machine. Now I am unable to sign in as the new Admin user, when I try to I get an error message and kicked back to the Windows start-up/sign-in menu.


I am unable to sign in as the administrator at all, or change the Admin rights back to the old user.


When I try to sign into the Command Prompt (Admin), it prompts me to enter the Admin password. I do, and I get the error:


"This file does not have a program associated with it for performing this action. Please install a program or, if one is already installed, create an association in the Default Programs control panel."


I am not even able to system restore, as I cannot sign in as Administrator. How can I fix this so that I can just go back to the "Mike & Steph" original user as the Administrator?


Any help would be much appreciated. I am very worried I have to restore the whole system.


Thank you!

It gets confusing if you ask the same question on two boards. I've answered on your other post...
Unable to sign in as System Administrator, "no program associated..."