rct3 soaked~keeps saying "wronge disk"?????

i downloaded rolercoaster tycoon and the expansion soaked. but evrytime i go to start it ill put in the rct3 disk and it says pllese insert rct3 disk. so i tried putting in the soaked cd but it still said pleese insert rct3 disk so i did again and it keeps popping up and saying that. does anyone know how to fix this? or am i doing sumthing wronge=S

rct3 soaked help!?