ZLIB1.DLL Missing?!

The game was working fine until yesterday. All of a sudden it gives me 'zlib1.dll missing' on startup. Tried to manually download the file and placing it into system32 and it seems to start but then it give 'Has encountered an error and needs to close'....


What gives here?! Suddenly it decides not to work anymore?

is this just civ4 or also an expansion? is this patched to date? did you ever install any unofficial patches?