try not puting nulls in screen color and try with sky_color. your .x file is maybe white because it doesn't have textures or...take microsoft directx model viewer (you ahve it with DX SDK) and if model is loaded properly it is fully .x file. i can't explain that but that's how i know. i had this kind of issue with irrlicht and .x file and I was advised to use that method.

hope i've been helpfull to you.