I have a problem with my RCT3 demo game I purchased from a book fair a year ago. It isn't a fake. I was dissapointed about this so I bought a full version of it. Same thing happened like the demo. So whenever I try to run it, an error window pops up and it says it won't run. Does anybody know how to fix it? Should I call Atari's customer service?

What are your system specifications? Test them at http://www.systemrequirementslab.com/referrer/srtest. Select RollerCoaster Tycoon 3 - PC from the drop-down list and see if you can run it. It's way more convenient then what we used to do by asking for DxDiag. If you can't run it then their's your problem. This might be the only solution, unless you did REALLY complicated stuff that might make it work. But that's too much to go through. So check on the System Requirements Lab to see if your PC is good enough to run the game.