Can't log on even though I'm the only user!

I downloaded CNN's pipline yesterday. It required downloading
Microsoft's .NET software. After that when it started up a sign-in
screen appeared. I had to click on 'new' to get in each time.

To avoid that I searched a computer forum and thought I found the fix.
I went into the control panel's user profiles and disabled log on.
After I hit apply a window appreared and I had to input a password for
administrator. I inputted a long time favorite. Also, going by same
instructions I went to Start, Run, and typed in something like 'user
service' and did something there according to instructions.

Now, however, when I start the computer it goes right to the sign in
screen saying I need a password. I thought that was to be eliminated
with what I had done, but I typed in my trusty password for
administrator. Rejected it!
Rejected without a password. Tried in safe mode with same results.

How can I restore this to the way it was before so I don't have to
clean the hard drive?

Thanks so much!