My original disc is broke but I do have a backup disc however when I try to play rct3 it says insert original disc not backup, is there a way to get around this?

please help
Thanks

No. There would have been various security features coded into the original CD image that are never copied over to another CD.

There are ways to get the game to run without CD's / Cracked CD's, but they are illegal and you will need to research that avenue at your own risk.

My advice would be to nip on out to your local software store and buy another.

Quick question: do you have RCT3: Wild! on your system? If so, you can run it off the Wild! disk, but there won't be any autorun, you'll have to use an icon. And if you don't have Wild!, I would buy it instead of buying a new RCT3 disk.