Urgent civ 4/BTS/Steam question

Steam has a sale on civ4 complete and individual x packs that, IIUC, ends at midnight.

I own a disk of vanilla Civ4, bought in a brick and mortar store. If I buy BtS from Steam, will they work together? Will I be able to run BtS even though I did not buy Civ4 vanilla from Steam?

different issue now. I am told they could, in theory, work together.

But Steam will not sell me BtS since they think I do not own Civ4. I do not know how, or if, I can register my vanilla Civ4 disc with Steam. I think I will have to bag this sale.

Unfortunately, Civ 4 is not one of the games that Steam allows you to register a hard copy of. I had the same issue, and I had to bite the bullet and buy the whole digital download pack.

I suggest first trying to see if you can get a hard copy of BTS somewhere. I believe it has all the features of Warlord built in, so you can safely skip Warlords completely.

FWIW, I got a pristine used copy of BTS from ebay for $8 shipped just a couple of weeks ago...it's not that pricy nowadays.

I have the Civ IV vanilla cds but I still bought the weekend sale $10 Civ IV Complete pack on Steam, mostly for Colonization (seems interesting, I never like getting to modern era in Civ IV). It was only $10, and it's convenient to not need my old cds anymore.