I haven't used the duplicate setting in a long ass time, but I've been trying to show PC games off to some friends of mine recently. However, when I have a m/kb game I need to see on both my monitor and the tv I have, using the "Duplicate" setting, which should show the same image on both screens instead stretches the screen in a weird way. It works perfectly find when I use the Extend setting, but for some reason it's not letting me duplicate. For reference, here's how the desktop looks like when using extend:

And this is what it looks like when using duplicate:

So it makes any game I try to run look super wonky. Duplicate should just show the same image on both screens, but instead it's stretching it. Also note that in the extend shot I just put up two different windows of GB -- it's not duplicating, since you see the start button on one side of the screen but not the other.

For reference I'm using an ATI Radeon HD 7870 with Windows 7 and an Intel i5 4670. Both screens are plugged into the video card.

Have you tried using the AMD Catalyst software to manage your displays? I haven't been on an AMD card in quite some time, but I manage my monitors through the Nvidia Control Panel.

It sounds like you have eyefinity multi-display turned on in the catalyst software actually, if you do turn it off.

This totally fixed the issue! Thanks!

No problem man, happened to me with my TV a few months ago