Installing retail BTS over Steam Civ 4

[AcesUpMySleeve]

I have Steam Civ 4 and bought a retail copy of Beyond the Sword. When I tried to install BTS it failed because it tried to install a patch on Civ and that failed, so it aborted installation. I tried setting Steam not to keep Civ updated with the latest patches, uninstalled it and reinstalled it. BTS failed to install with the same message. When I had a look at Civ 4's properties it was set back to be automatically updated with the latest patch.

Is it possible to install retail BTS over Steam Civ 4? Any ideas?

Thanks in advance

[Europhoria]

You need to buy the expansion from the Steam store, it won't work with the retail version unfortunately.

[AcesUpMySleeve]

You need to buy the expansion from the Steam store, it won't work with the retail version unfortunately.

Hmm, that's annoying. Ah well, thanks!