SweetFX v1.4
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d3d9.dll, dxgi.dll and injector.ini goes into /common/half life 2/bin
the rest goes into /common/half life 2 and disable in-game AA
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SweetFX v1.5.1
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Extract SweetFX into the following directory = \Steam\steamapps\common\Half-Life 2\bin\
You do NOT have to disable AA in-game
-Omni