Same issue. Went from Windows XP to 8.1 and no longer have the box. In regedit, my Red Alert folder was under Westwood but it didn't have anything labeled /ergc. I went with the only 22 digit number I could see in that folder but the new installation wouldn't accept it (I also had a different product key # from an old regedit file from my last computer update (Windows ME to XP), but that # didn't work either).
Any other thoughts? The discs are original. The game is still installed on the XP computer.
Thanks!
Shannon