Importing SMD in Xtreme3D

If you're using 3dsmax 5,6 or 7, have a look at this.
First, you load up the reference file (the actual model with bone structure):
actor=ActorCreate('reference.smd',scene);
Then, add the animation files (the files with the animation for the bones)
ActorAddObject(actor,'animation_idle.smd');
ActorAddObject(actor,'animation_walk.smd');
ActorAddObject(actor,'animation_run.smd');
ActorAddObject(actor,'animation_jump.smd');
Then, you can switch animations using ActorSwitchToAnimation(). You use it like this:
ActorSwitchToAnimation(actor,2);
The 2 indicates the loaded animation, which in this example would be animation_walk.smd, since its the second animation loaded. If you would like it to load the run smd, just use 3. If you want it to go to its starting pose (the one it was when you saved the reference file), just set it to animation 0.
If you want to know what animation it is currently playing, just query ActorGetCurrentAnimation(actor), it will tell you the path to the currently playing smd file sans extension (it will say animation_walk for example, or res\model\animations\animation_walk).