My Dimension 8400 has an x300 video card. I typically use two monitors, but have recently wanted to use a TV as a second output. I do disconnect the secondary monitor when I am trying to connect to the TV.
I am using an S-video to RCA converter and then RCA/RCA to the TV set. This setup does not display a picture on the TV. I've tried both the standard video properties dialog and Catalyst (2 versions) to configure the dual displays without any luck.
I use the same S-video to RCA Converter and then RCA cable to the TV with my Latitude D610 with integrated video and it works fine.