My LED TV won’t connect with my PC

I am very happy with my LG Series LE5500 32" (32LE5500) LED TV. I use it with my Xbox360 connected via HDMI cable.
I am just worried that something may be wrong with it because every time I try to connect my CPU via HDMI it shows nothing.
I already updated my drivers but it's like the TV doesn't detect my Graphics card. What could be the problem?
