Help, computer does expansion does not recognize Roller Coaster 2?

I have Roller Coaster2 with the Time Twister Expansion loaded to my computer from disc. No problems with it at all. Last night I downloaded the Wacky Worlds expansion pack from Game Stop. When I try to install the new expansion pack, the installer can not find the original Roller Coaster2, even when I try to save the new expansion into the original Roller Coaster 2 folder. What am I missing here?