I'm fairly sure that the apple thunderbolt to HDMI adapter would be perfect for the job, although cheaper alternatives are likely also available? I use a thunderbolt to DVI adapter to power a second screen on my Macbook Air, and a thunderbolt to HDMI to connect my Mac Mini to a TV so I'm fairly sure that this would work for you too.
Alternatively I'm also using a couple of these Displaylink http://www.amazon.com/Kensington-Universal-Multi-Display-Adapter-Black/dp/B002F9 NSMQ from a USB hub to power an additional two screens (via HDMI or VGA) giving me three 1080p screens plus the laptop screen all running from my 2011 Macbook Air. It is the envy of the office!!
Hope that helps?
Almost! xD I'm wondering something, maybe my question was confusing, I want to use the tv as a second screen, I mean, like this: (but with the mac and the monitor I linked)
Is it possible or it will just send the iMac screen to the TV screen?, know what I mean?, I think I can't explain myself
Sorry for the delay in replying back to you Enemmy.
You can do both. Once you've got your second screen connected to you iMac then just right click on the desktop in Windows 7 go down to Screen Resolution and make sure under the 'multiple displays' option select 'Extend desktop to this display'.
Then you're all set.