XnView Software

I want to use NConvert in 32 bit mode, as the lossless JPEG plugin only works in 32 bit mode. I want to do this because cropping an image with 95% quality produces images that are larger in size (and slightly less in quality) than the original would have been had it been losslessly cropped.

How would I force 32 bit mode for nconvert with Mac (10.7) and Windows (7)?

For windows download the 32bits versions.
On Mac, you have not the jpeg ls plugin