Want to play videos from computer on 40 in LCD TV

Hi. My ultimate goal is to be able to play videos from my computer on my 40 in LCD TV. I was going to buy a DVI to HDMI adapter, and a 20ft HDMI cable (my TV is pretty far away, and can not be seen when sitting at the comp) and a 20ft audio 'Y' cable, but I realized I would just be adding a second monitor. I don't want a second monitor. I don't want to be able to drag windows over to the TV all the time, because I can't even see it from where I am sitting. Basically, I want to have the TV as a second monitor, but only when I am viewing videos on my computer. When I am surfing the internet, typing a document, playing a game, or using photoshop, I do not want a second monitor. If I don't check the box that says "extend my desktop onto this monitor" the screen is blank. Is there a way to switch between one or the other monitor at a time, or can the TV duplicate what is on my monitor, cause that would be choice. I remember on Dell laptops (which I used to support) there was a hotkey for switching between your screen, a second screen, and both screens with the same thing on it. I would prefer that a video signal is only being sent to the TV when I have that input selected, in other words, I don't want to clone the screen when I am typing a document, even if the TV is recieving from the cable box, and not from my computer.

anyway, any help is appreciated.

Thanks

It's all on your vid card control panel, under display settings.

You can set it to be dual monitors, only on one, or as said above, with the same output on both screens.