New User Account removed MY administrator access to safe-mode only

Last night I made another user account on my PC. I was a bit perplexed as to
why I could not limit the user account and had to make them an administrator
level. This morning when I turned on my machine I figured out why (after some
research in this support section) -my normal log-on administrator account
disappears once ANY OTHER USERS ARE ADDED TO THE SAME MACHINE, unless one
starts in safe mode!!!

I am curious if there is
1) ANY WAY to now remove ALL other user accounts (except for the default
administrator, my normal account which I unknowingly over the last 16 months
have made into MY personal user account) or ...
2) to remake and copy EVERYTHING about the default administrator user
account over to a new administrator account so that when I start up my
computer I can log in normally and even with other user accounts on the
machine vs. in safe mode, which is absolutely useless- I don't even get my
monitors in safe mode.

Thankyou!