Greetings all..With the new patches that are out, there always seems to be some problems with some people updating while others have to wait because of pbem's or other games that cannot be loaded with a new patch. This becomes more of a problem when a new expansion like BtS comes out, because installing BtS automaticall upgrades to the new patch.
The Dual Install is a good solution to the problem.
---------
If you have purchased BtS but have not yet installed it, these are the instructions to be able to play with both versions:
1. Copy "Sid Meier's Civilization IV" in Program Files/Firaxis Games, to "Sid Meier's Civilization IV v1.61". (You can just copy the folder right next to the original. It will take several minutes to accomplish usually)
2. Rename "Sid Meier's Civilization IV" in My Documents/My Games, to "Sid Meier's Civilization IV v1.61".
3. Install BtS.
4. Run from one directory or the other to get the version you want. You'll also be able to install mods separately for the two versions, save games will be separate for the two versions, etc. The new version will have a clean install with no mods, which is probably what you want (since many old mods won't work).
If you have Warlords, you don't have to do anything other than the above steps. There is a seperate Warlords folder in each of the folders represented above. For 2.08 (or any older patch), go into the Warlords folder in the CivIV 1.61 folder above and click the .exe file to start that game. (you can also copy that .exe to the desktop and rename it Warlords2.08 so you don't have to search folders for it)
For any new patch that you have loaded, you would click on the installed shortcut on your desktop or go into the original folder represented above to click the .exe there.
-----------
If you have already loaded BtS and would like to be able to revert back to a previous version there is a way to do that, but it can be "iffy" and I would suggest the following:
1. Completely uninstall CivIV Vanilla, Warlords, and BtS. (While copying any game saves you wish to keep in another folder)
2. Reload CivIV Vanilla and Warlords and repatch to the older patches you wish to play with (1.61 and 2.08 in my case)
3. Follow the steps listed above for a pre BtS Dual Install.
I know that the uninstall/reinstall takes a while, but it saves some headaches...
Thanks to our friends at Civfanatics for helping with the process. 
