The problem is there are two Space Rangers 2 - Dominators and Reboot. Now if this one on GOG is not the one you played…
EDIT:
Checked GOG forum and buyers are not happy. Seems that SR2
ominators on GOG doesn't work on win7 x64. They however got SR2:Reboot (available on steam, gamersgate, etc) and that one does work on their machines. Although they needed to force windowed mode. But playing in windowed mode doesn't exist in Dominators at all. SR2:Reboot is a standalone game that includes Dominators and more additional content.
So I'll skip this one on GOG. Sorry.