You cant load the format that you are asking about because it is not supported natively by DarkGDK. The simplest thing to do would be to find a file format converter that will convert that format into something that GDK can read, but if you really wanted to use that format, you could write your own loader for it, though doing so is a very complex subject and requires a high level of proficiency with both 3D graphical techniques, and c++ programming.
Im also not sure what you mean by "animation" ... is it a model that contains animation ? or is it a motion-capture type animation containing only data about the animations(no model data) or is it a DVD type animation ?(the command you are using above is actually broken, but they are designed for playing video, if you do want to play video, serch the forums, a user called Video Playback posted some useful code to play dvd's and videos from inside GDK.
If it ain't broke.... DONT FIX IT !!!