need help with game update w/o CD

[Poliet]

Hey folks, great forum here...

I got a tricky question for ya..

I got this great game, civ4 which runs fine w/o cd on my backup computer. ;P I want to upgrade my civ to the latest version since the original version chrashes a lot. When I download the patch to civ 1.59 and run it, windowz pops up telling me that it cannot find a previous installation. Please install the game to run the patch blah. How can I fix that without installing the game. My original CD has a nasty scratch and you can guess that I cannot make a new installation anymore
Is there a way to tell windows that an installation of civ4 exists, so that I can run the patch and upgrade my civ4?

Thanks