BMP, or BitMaP, is the standard file format for storing bitmapped images on the Microsoft Windows operating system. Fractal eXtreme stores its fractal files in BMP format, so that the images can easily be used in other programs. BMP files typically have .bmp file name extensions.
However, some programs do not properly or completely support the reading of BMP files and cannot handle reading Fractal eXtreme files directly.
Fractal eXtreme stores all the fractal information it needs to save (location data, bitmap data, palette data, and possibly more) between the header and the actual bitmap data in a BMP file. This is a perfectly legal variant on the BMP format, but many programs have problems with it. Also, the bitmap data is stored compressed, to avoid wasting enormous amounts of hard drive space. Although storing images compressed on disk is clearly the sensible thing to do, many programs to not support this variant of the BMP format.
If your favourite program that deals with BMP files does not load Fractal eXtreme files properly, complain to the vendor. Or, alternately, use the Save Bitmap Only command (in the File menu) or the Copy command (in the Edit menu), both of which create BMP files that are optimized for compatibility.