UAC not letting me enter an admin password

I'm trying to run my main user account as a non-admin, but any time I try to
perform any admin task, the UAC prompt tells me I have to enter an admin
password and hit OK. The problem is, there isn't any textbox to enter a
password! OK button is disabled (I guess I should expect since I haven't
enetered a password), but how am I supposed to perform any admin task? And I
can't log in as an admin because it doesn't show on on the welcome screen.

> I'm trying to run my main user account as a non-admin, but any time I try to
> perform any admin task, the UAC prompt tells me I have to enter an admin
> password and hit OK. The problem is, there isn't any textbox to enter a
> password! OK button is disabled (I guess I should expect since I haven't
> enetered a password), but how am I supposed to perform any admin task? And I
> can't log in as an admin because it doesn't show on on the welcome screen.

What a cool dialog! I am guessing you went into Computer Management and
removed your account from the Administrators group? The reason no
administrative accounts are showing up in the dialog is because there are
none! You removed the last operational administrative account on the system.

To fix it boot into Safe Mode by holding down F8 on startup. It should
automatically log you in with the Administrator account (which is disabled
normally). Then add another account that is an administrator. If your regular
account is not an administrator you need another admin account to elevate to.
The OS will prevent you from removing the last admin account if you use the
Users control panel, but not if you use any other tools.