if you are using galaxy forge 3 with sins 1.15/entrenchment then you MUST use the program files/stardock games/sins of a solar empire/galaxy folder
for earlier galaxy forge ie 1.1 which uses map format version 2 the maps do not show up because 1.15 does not know how to read v2 maps any more, BUT I did write a map updateing utility that updates all version 2 maps to version 3 so you can play all older maps. it can be downloaded here sins_map_updater_v1.1.8.rar it looks for sins version 1.15 and will work on non-english windows as well as english language windows ie xp,xp64,vista 32, vista 64,windows 7 32 AND windows 7 64 bits
hope it helps
harpo