I used this tool with Arma 2. You can go to the Windows desktop, change the settings and return.
http://www.assembla.com/spaces/fxaa-pp-inject/wiki
http://www.assembla.com/spaces/fxaa-pp-inject/documents/cyPOIUECGr4BM4acwqjQYw/download/cyPOIUECGr4BM4acwqjQYw
First , turn off the settings for the FXAA - there is FXAA in game in some addons of Arma 2 and also in the last drivers of Nvidia , more advanced and ajusted with Arma 2 - . Also turn off HDR, the bloom, the Technicolor and color correction to work properly and only use the sharpening settings and the tonemap. So you can change subtly shapening and the tonemap and near to art style of the game . Then if you want to make bigger changes can try the HDR, the bloom, the Technicolor and color correction but overall the results are greatly exaggerated.
Sorry for my english lenguage mixed of my knowledge and google translation :)
Screens - only with sharpening and tonemap tweaked -
http://i4.photobucket.com/albums/y117/jonelo/armad%202/arma22012-05-0501-32-09-15.png
http://i4.photobucket.com/albums/y117/jonelo/armad%202/arma22012-05-0501-32-05-64.png
http://i4.photobucket.com/albums/y117/jonelo/armad%202/arma22012-05-0501-30-55-87.png
http://i4.photobucket.com/albums/y117/jonelo/armad%202/arma22012-05-0501-32-23-43.png
http://i4.photobucket.com/albums/y117/jonelo/armad%202/arma22012-04-2816-15-52-66.png
http://i4.photobucket.com/albums/y117/jonelo/armad%202/arma22012-05-0501-34-02-23.png
http://i4.photobucket.com/albums/y117/jonelo/armad%202/arma22012-05-0501-34-37-77.png