Can``t view movies from my laptop on my TV

Hello,
I recently connected my HP dv2000 laptop (XP operating system) to my Sony HDTV. When I turn on the TV I see my 1/2 Desktop on the television screen, even though im playing and can see a movie on my Laptop. In short i cannot view movies playing on my laptop on my TV even though the Laptop desktop shows up on the TV screen. Oh ! I am using HDMI cables forthe connection