Unable to find the elements related to window


I am novice to ruby ,I am using to test my application.My problem is
that if you can see the attachment when I try to create a new GUEST ,a
new WINDOW DIALOGUE appears and where I am not able to use IE Developer
tool bar where the window only becomes Active and I am not able to
identify the fields related the
Web Page Dialogue(Valid Login ).where I able unable to fill the username
and password dynamically at this situation as it appears in New dialogue
box.Can you let me know the reason.
If any please let me know ASAP.

Thanks in advance