'DivX 4+ properties' is gray (disabled).
 

In fol screen the image get very pixelated. I want to activate PostProcessing but the 'DivX 4+ properties' is gray (disabled).
How do i make it work again.

I have FFDShow and DivX installed.

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It happens just in full screen. If the video is windowed, the image is smooth.

That window is legacy. In the eraly releases of BSPlayer, when a video file was loaded and one of the codecs in that window was in use, you were able to modify properties. Not any more.
If you have ffdshow installed, probably it's used to decode most of the video files, so START -> programs -> ffdshow -> ffdshow video configuration

Solved:
I switched to Internal Render Direct Draw.