SEPM Domain Authentication

I had our SEPM linked to our primary domain controller and had all the admin user accounts tied through that. One of my IT members demoted the primary controller without me knowing, and now I do not know how to log into SEPM to change my domain controller. Every username and password that I have tried comes back with an errro that says "the administrator's username or password is incorrect. Type a valid username and password."

Is there some registry hack I can perform to change the IP address and point to our new primary domain controller? Thanks.

-Storm