Omega Driver and theater mode

JUL35

HI,
I have a problem and hope you'll can help me:
I have a live video program (Resolume) which can use the dual monitor mode (displaying a video ouput to a TV for exemple and keeping a little video window on the user interface, which is not possible without that mode).
I've seen on a live video forum that ATI cards was able to use this function by installing last omega drivers and switching in theater mode in the overlay options of the ATI card.
I've got an ATI Radeon Mobility 7500 running on a Dell Inspiron 5100 so that's what I did and in fact the theater mode is only available when no video ouput are connected on the laptop
so, how can I make theater mode working with a video output connected?
thanks