^ pretty much, even though technically HDMI can be used for bi-directional communication.
For what you want to do you need a dedicated video card that can output to at least two monitors like a Radeon 4350. Connect your TV with HDMI, and connect your current monitor with a DVI or VGA connection. From there go into your display settings and set it to mirror the outputs.
marzuki, did you change the display type in display settings, some cards can't detect when HDMI is connected to screens to change the display automatically. sometimes we need to change this manually ( it's not the card really but driver versions that we use) and it's not one videocard company, it's all, just has to do with certain driver software. I noticed that when using the software that comes for your cards everything works fine, but when downloading newer or different driver/software for the cards you may need to change settings for other video outputs to work correctly.