I need to take a running windows desktop box that's part of a domain, give it a new computer name, and then continue working on it (with the box having the new name), without having to reboot at all.

Thats not your user name, it's your profile, it honestly can be ignored, it doesn't reallly do anything. If you want, you can try to delete the profile, then login again to have it make a new one. It ...

Officially changing the Department of Defense to the Department of War can only be done by Congress and would require ...