I need help getting a downloaded game to play

Hi everyone, I downloaded Roller Coaster Tycoon 3, which seems like everything it needs is there, i can either install from the files or also from a copy i made on disc. It completly installs with no problems which gets you so excited about playing then once you click the icon to play it a message comes up asking for me to insert the actual disc for the game. I know its something to do with a crack but have no idea what to do

please help some one

 

you are right about cracks, however the forum rules forbid us from talking about them. you'll have to try your luck by good ol' research, instead.