Installing BTS Disc Version to Civ 4 Steam -_-

[astrosoup]

I got a disc copy of BTS for birthday or something, but I lost one of my original Civ4 discs so I just bought the game on Steam.

Steam gave me an up-to-date version of Civ4, but of course BTS installer wants to patch anyway, fails, then aborts, crashing the whole thing to desktop:

Can anyone here help me get around this? Thanks a million.