Yes. Did you change the name of the Hidden Admin? If you cannot now enable it I'd run SFC -SCANNOW Command
to make sure no System files have been damaged.
I'd rename the Computer to the one of your choice at Computer>Properties.
Even if you change the User name as you've done the original User name will hang around for some arcane security reason until your run Factory Recovery or reinstall.
As you're obviously already well-versed and eager to learn you might want to get the superior Clean Reinstall now: Reinstalling Windows 7