[otrs] Admin button gone for root@localhost

I've been 'playing' with OTRS 2.0.4 (installed on a Windows platform). Logged in as root@localhost and through the Admin menu, I setup many system-wide settings. I rebooted my server, logged in again as root@localhost and the "Admin" button has disappeared! Aaahhh, now I can't continue with the system setup - what have I done wrong and how can I fix it? Many thanks for your help.