Originally Posted by ATI's help section
..Video Overlay is unavailable on secondary display adapter:
In general, Video Overlay will only be available on the primary display adapter. If the TV Tuner is being used with a secondary adapter then the overlay feature required by the ATI TV Player will not be available.
To correct this, the display adapter must be configured as the primary display. Check with your motherboard owner's manual for ways to configure your display adapter as PRIMARY in the motherboard BIOS setup.