How was the jerkiness in HL2 resolved in Vista again?

[DEATH eVADER]

I thought this hotfix would of been installed with either SP1 or SP2, but I guess it didn't. I have a problem which revolves around unstable FPS in HL2 (Yeah playing through it again).

L4D and L4D2 run fine; haven't installed Orange Box games to compare so I'm guessing it has something to do with the earlier build and the incompatability with Vista (which there should be a hotfix lingering around for)