I fixed it, and I've never been happier! I've never been so excited to see the Start menu, ever.
I even had to run this old copy of BartPE that I found in my stack of CD's.
And then when it didn't work, I was looking into what backdoor it might have been. I needed to look at the CounterSpy log file, but I couldn't. I navigated back to the Userinit registry key and realized I misspelled Userinit.exe.
I had typed in Userint.exe instead. I changed it, and it worked!