HELP!! User issue

[zer0halo]

I think I really blew it and I don't know my way out. When I installed
Ubuntu I set up my user name, which I'll call "newlogin". However, I
had previously used a different user name, and had shares on a remote
server which were accessible by my former user name "oldlogin".

So today I needed to access those files, and in Ubuntu I went into
Users and Groups and decided to go into my "newlogin" user properties
and rename it back to "oldlogin" (stupidly, instead of just creating
another user).  Everything seemed fine until I tried to run sudo and
got the error "user oldlogin not in sudoers file". Yikes. So because
root is disabled in Ubuntu I can't get into root to change my user
name back to what it was or to edit the sudoers file. Nor can I run
any program that runs at root. So I'm stuck. I guess that's one
disadvantage of having root disabled. Is there any way out of this
besides having to reinstall from scratch (which I really don't have
time to do!). Thanks for the help.

-- 
"Impossible is nothing."