I posted
here a .blend file, which is also quite common, with a short manual for posing. It would be cool if you can post it in both .blend and .3ds.
It's handy in Blender, you can just define the first and last keyframes with A+A+I+LocRotScale and it computes the animation in between, when you start the animation, you just have to adjust the "keyframes", if the automatic animation looks not as you wanted.
It should suffice for test work and Blender is free. However, currently, only Blender 2.49 can export/import .X files.
The IK constraints i put in the legs of the model are also handy for posing since you can grab and move the ankle and see the whole leg bend in appropriate direction, instead of adjusting every single bone. The arms needs them, too.
In the end, we should be able to convert everything back to .X, which program does it best, we should test out.