[Zacker]

I have a powerful machine which runs all other games well, but it just dont like HL2.

I have found that the following settings give the optimal results for my machine:
800*600
medium models - High really kills my machine
high textures - Medium is ugly and high dont require much more
high shader - Parallax&normal mapping is a must
high shadow
reflect world
2xaa - dont improve much and dont require much
2xaniso - dont improve much and dont require much