easy way to tell is to right click on the desktop and get to the display settings. then go to settings tab, and then advanced. there should be a tab or something called displays. tv should be one of them.

the tricky part is that it's hard to see regular computer stuff on the tv screens. you can do powerpoint, or video files, but regular applications tend to be too small to read easily. (although, new flat screens or plasmas may be different).