I formatted my PC so I had to reinstall Civ3. The Installation process gets to where the installshield is about to open and then a message comes up sayin something in the like:

Cannot open DSETUP.dll

What do I do?

You may have a very dirty/scratched CD. Try rinsing it in water and wiping it dry with a dry cloth.

are you freakin' crazy? WATER? of all things, one of the evilest to CDs is WATER.. skip the water and try a dry, lint-free cloth.