Hi yxurr! this is not really an answer so i'm writing a comment. skeletal animation is basically the same whatever your using so you should be able to just find a tutorial on animation and change it up a bit to fit with directx. I've never used Assimp before, but once you have the model loaded in, you should be able to just follow any directx tutorial on animation to get it animating. It's been so long since i've used dx9 so can't help you much with specifics. basically there are two ways you can do animation; the first is updating the vertices in a vertex buffer based on the rotation of the bones, then uploading that changed vertex matrix to draw. This is slower than the other way since you are uploading an entire vertex buffer every frame. The other way is to upload a list of matrices that you have calculated for each bone, and multiply the vertices in the vertex shader by the ones based on the weights the vertices have for each bone. This will be much faster, but is a little more difficult to get set up. Then again though, dx9 has a fixed function pipeline doesn't it? anyway, heres a link to a book that might help you out: https://books.google.com/books?id=8Y4VrGBtGM8C&pg=PA248&lpg=PA248&dq=directx+9+skeletal+animation&source=bl&ots=pV4DdSsjt4&sig=Jy8euoLxd0AYa8wvkY2r9lSDfI0&hl=en&sa=X&ved=0ahUKEwjl5q_8483MAhWEGx4KHReRCg0Q6AEIUzAH#v=onepage&q=directx%209%20skeletal%20animation&f=false

Thanks for the comment. I think the best way is to learn OpenGL and forget DirectX 9... I like DirectX 9 that's why I tried to fix it without OpenGL but seems to be quite hopeless. And OpenGL is always good to know.

Hey! What's your computer specs? Maybe you can run win7 and use directx11.