You can write an interposer DLL to implement DX3. It's a simple-enough API. But there will be some key pieces that will ruin the end result, either for performance or entire functionality. My suggestion is to try to translate DDraw to WinG as it should offer more speed and game-needed features than stupid GDI. And I guess forget about any HW-accelerated color-keyed blits, it would be all done in software... so don't expect matching perf to Win95.