Format of the file <X:\TEST.DWG> could not be determined
For display of less common format, the following option is available:
Options>General>[x]Display all image file typesWould you like to continue?
[ OK ] [ Cancel ]
This setting is enabled, and CADImage.dll is installed properly.
I know for a fact that I was able to generate an HTML gallery for files of this format about three years ago with older versions of XnView and the CADSoftTools plug-in.