I delete myself from administration. What to do?

When I download some update, after install, I always need to check box "Which
user account do you want to use to run this program?"
I tried to turn that off, and I didn't know how to do that..and I do mistake.
In my computer was 2 administrators, me and name"administrator". I tried to
delete name "administrator" and couldn't, but, I tried to delete me, and I
did it! LOL. Name "administrator" was disabled before I delete me, and after
I delete me, administrator is still disabled, but I'm now only user and can't
do anything (update,...)

QUESTIONS:
1. How to put me back in administrators
2. How to delete name "administrator"
3. How to disable that popup what I see always when I open some program

I'm not so good with computers, so, please tell me details how to do
something if is possible

Ty