well i know all about the nvidia ones, either way try this:
right click the desktop and then go to properties, then click settings, followed by advanced....then, depending on the chipset and wiether or not you have the drivers installed, there should be an ATI or Nvidia display tab with a company logo, somewhere under this tab you should be able to find something about auto detecting a tv, you may have to manually have to switch over due to the fact that some chipsets only support tv or computer monitor at once, sum wont let you view both at the same time.....