few years ago I tried to install GC on my new XP machine and found it claiming to be no original.
it installed properly and accepted the CD key, but did not run.
same disk worked under 2Kpro before.
I suspected the disk to be damaged and stopped trying.
1-2 years ago I bought the Gold CD and installed it.
it ran properly but the gameplay was changed to crap (scientific advances did not apply etc.) so I stopped playing it.
recently I thought I'd like to play it again and bougt a new disk of the first version via amazon marketplace.
I experienced the same issue: the startup told me the disk was no original. Link
please advice help asap, I think it's legitimate to want to play a game I payed for three times.