1. Is the TB a USB drive? describe the setup as best as possible.
2. At the logon screen press CTRL+ALT+DEL simultaneously: Does anything happen?
3. Right after the BIOS post, press F8 every second and select Safe Mode logon.
If you manage to logon in Safe Mode apply these settings:
http://engtech.wordpress.com/2007/03/20/windows-xp-logon-screen-with-no-user-accounts/
Report back if anything worked or not.