O.K., I'm the guy in question, so I thought I'd chime in here.
Points of clarification:
I do have Desert Siege, have it installed, can play it, and even finished it before I reinstalled. Reinstall included uninstalling DS and GR, installing GR and DS, and patches 1.3 and 1.4. I have no other instal of GR on my computer.
Any help would be greatly appreciated!