DazStudio is OpenGL based. OpenGL is the only realistic cross platform graphics API. DirectX is pretty much a Windows only affair. OpenGL is also a whole lot easier to code. DirectX is a horror. As to performance differences between OpenGL and DirectX I personally have never seen anything significant enough to outweigh the cons of dealing with DirectX. Although a lot of games are going to DirectX, at the higher end of the graphics hardware and software spectrum, OpenGL pretty much dominates. The new OpenGL 2.0 spec will also level out the differences between OpenGL 1.x and DirectX 9 and above. Windows XP and 2K share a lot of common core code and 98/Me are close to that core. Under the hood where you are actually writing lines of code Windows 95 has a number of "issues", some age related, that made supporting it a problem.