[Stiglr]

You got me there. I don't even know what XP refers to, outside of an old Windows operating system.

That would fall under the realm of interfacing with an export software. For every outside application, there's a new set of hurdles. In my case, for some flight sims I must have triangulated surfaces, or an object won't display at all; for others, that's not an issue. And how they receive and display both materials and textures varies widely (some have a very limited selection of graphic formats that textures can be, and some have strictly defined graphic dimensions, such as "only square graphics, power-of-two dimensions, such as 128 x 128, 256 x 256, 1024 x 1024". Perhaps scour the documentation for your end destination for a solution. It may be that you might need to pass your model through some other 3D tool (like, say, Blender) and then the materials problem will be fixed during the transformation. Worth a try.

Or, try exporting FROM AC3D as some other file type than .ac. That might accomplish the same thing.