I think it might actually store an encrypted form called a hash..?
Edit: UT2003 is in the following location by default:
HKEY_LOCAL_MACHINE\SOFTWARE\Unreal Technology\Installed Apps\UT2003
Since 2004 was just an upgrade of 2003, it might be in a very similar location. I'll keep looking for info
2nd Edit: Found a source that says UT2004 default is:
HKEY_LOCAL_MACHINE->SOFTWARE->UNREAL TECHNOLOGY->INSTALLED APPS->UT2004
[This message has been edited by FieroGT42 (edited 01-16-2007).]