I have Steam, yes, but don't have Civ4 via Steam. I do have five Civ4 disks lying around though:
One just Vanlla
One just Beyond the Sword (or maybe Warlords too? Don't know.)
One Colonization (never actually played it though)
And two Civ4 Complete
I guess I could buy Civ4 on Steam too for good measure though.
One or two of those disks probably don't work anymore because I spilled hot chocolate one day, and I don't know where exactly all of them are in the mess of my room. Wouldn't actually mind paying again for it though, Civ4 is just worth it.* (Compare with Civ5 where even buying it once is one time too many.

)
*Ironic then that I originally pirated BtS and only actually bought it after it messed with PBEMs.