Connecting Laptop to TV with HDMI Cable?

Went to PC world the other day and asked how to do it ( as the TV I bought from them, as sony Bravia flat screen 32" advertised this capability.) They pointed me in the direction of this HDMI cable, which sure enough plugs into both my laptop, and the TV. Great. I plugged it in, hit the home button on the TV and found the correct input ( AV2 I believe) and switched the TV to that. But aside from my laptop losing its capability to project sound while the two were linked, nothing happened. I have seen various videos on youtube and some say you need other cables like VGA leads ect... but the man at PC world said otherwise, and other vidoes show it being done with just the HDMI cable. How can I complete the task I started and watch Russel Crowe's Gladiator on my TV using my Laptops DVD Player.