i cant understand.

how do they get like 80fps in half life2 with radeon9800pro, im getting like 10-20 with maximum setting, 0xAA  8xAF :/

my machine:
P4 2.0
dual channel ddr 512/400*2
poworcolor radeon9800pro 128mb 256bit

does cpu have anything to do with that?

I'd expect people would get 80fps in HL2 using a 256mb r9800pro instead of a 128mb, and using a faster processor. They probably run the game at lower settings as well.
The odds of you needing 8xAF are... well... low. Try lowering that, unless you definitely think you're seeing a huge difference with it. (possibly try AA?)

Additionally, I never really saw much of a purpose for vsync, so maybe try turning that off. Additionally, try benching yourself when you're past the airboat part. That mean old helicopter rapes most graphics cards through the water effects. :x