Have you tried entering your CD-key into the Steam "add a steam product option"? I got the disk many years ago as well but got the steam version by entering my CD-key. This works for a suprisingly large amount of old games that have been ported to steam.
Comment History
Ludde016 - - 3 comments @ Divide and Conquer
Good karma+1 vote
Ludde016 - - 3 comments @ Estranged
Good karma+1 vote
I love this mod! and the game is not even done yet :3
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Ludde016
Ludde joined
Mods for the win.