I just formatted and reinstalled windows xp along with Giants from gog.com. When I go to launch the game, I get a blank error titled "Giants Error" and two buttons "OK" and "Cancel".
The only way I could get around it was to patch the game to 1.4 and then use this no CD crack located in this thread.
http://www.gog.com/en/forum/giants_citizen_kabuto/patch_makes_the_game_ask_for_the_cd
Thought someone might like to know :)