Note: The content in this article pertains to ArcGIS versions 9.x and 10.0. Later versions of ArcGIS may contain different functionality, as well as different names and locations for menus, commands and geoprocessing tools.
When exporting from ArcMap to the BMP, JPEG, TIFF, PNG and/or GIF format, the 'Write World File' export option is grayed out or unavailable.
The ArcMap export dialog was accessed while ArcMap was in Layout view.
ArcMap cannot designate spatial references for the entire map layout, only a data frame, so this option is only available when viewing only one data frame.
Switch ArcMap to Data view by navigating to View > Data view and then navigate to File > Export map. The 'Write World File' checkbox should now be available when one of the above exporters is selected.