Good luck, hope you can get it working.
I noticed a few extra benefits of dgVoodoo that make it worth using on earlier versions of Windows as well - with it installed Machines is displayed in 32-bit colour mode instead of 16-bit, and you can force bilinear/trilinear texture filtering for all textures (through the dgVoodooSetup utility).
32-bit colour massively improves the appearance of terrain and sky textures (especially darker colours / at night) by reducing banding.
Forced texture filtering reduces the jagged appearance of distant / angled textures and smooths over certain textures which Machines usually renders with nearest-neighbour sampling. This causes slight distortion of some transparent textures (e.g. autocannon turret barrels) and parts of the interface. I think the trade-off is worth it - especially if someone makes higher-resolution versions of the affected transparent textures (which would reduce the visible distortion).
NOTE: If you use dgVoodoo 2 2.55 or later with forced texture filtering, set the "Videocard" under the DirectX tab to one of the GeForce cards to avoid pink outlines on some transparent textures (gun barrels, etc.)