If you own a physical copy, you are legally entitled to a backup ISO and a No-CD patch.
In the context of retro gaming, an "ISO" is a digital image of the entire game disc. Players would often download the RCT3 PC-ISO to reinstall the game if they lost their physical copy. To use these, players utilized software like Daemon Tools or PowerISO to "mount" the image, tricking the computer into thinking a real disc was inserted. If you own a physical copy, you are