Retail Windows CD Key on a MAC?

[duosoft]

I have purchased the boxed retail version of Civ4 for Windows.
I would like to play it on my MAC via Steam.
Is it possible to add the CD Key to steam, and download CIV4 via SteamPlay for the MAC, since it is available for steamplay?

Or do i have had to bought Civ4 for windows on steam, for the cross-platform thing to work?

[RABicle]

Dude, people who own Civ4 for windows on steam can't even play it on Mac, despite the claims of steamplay.

At least you have to option of buying it again (get the complete pack) some of us can't even do that because Steam wont let us own a game twice.

[DKill3r]

Only the retail games mentioned here can be registered on Steam: https://support.steampowered.com/kb_article.php?ref=7480-WUSF-3601

But they expand the list from time to time.:)