Rollercoaster Tycoon 1 really weird problem

I haven't had any problems with it untill now. I finished a bunch of senarios and took out the disk to play a cd, and when I put the disk back in, everything is gone. No saved senarios, no saved rides etc. I saved everything and have closed and reopened the game and shut my computer off many times without problems before this. Only when I removed the disk from my computer did everything reset. So.. do I have to do everything over again, or has anyone heard of this problem before; is there some sort of patch?