Portmaster is a utility that will change a Marathon 2 map file for the Mac and make it usable by Marathon 2 for Win95. It can also change an Images file into the image.img2 file, as used by the Win95 version of M2.
This utility is not supported by Bungie and is to be used solely at your own risk.
Helpful Hints:
Make sure it has as much memory as you can give it.
If you have pictures in your map file, make sure that they are all 8 bit as 16bit images may crash the application or have other horrible consequences.
Result:
A new map will be created: "New Map", rename this map so that it has the extension .sce2
A new images file will be created: "New Images", rename this file so that iy has the extension .img2