VBGamer

I'm making a game using d3d7 and vb,i load md2 and x models using the engine i wrote for the games,first when i tested the rendering of the engine by voodoo cards it works properly,but when i tested it with an ATI Rage card the x files redering becomes bad the are redered from back first the front polygons and the md2 have the same problem too,and the x files apears behind terrains. Please can anyone tell me what causes this problem and how can i solve it? Thanks,