So I just got Riven and RealMyst. Neither of them have worked for me.
Riven crashes before the Icon even loads in my Toolbar.
While RealMyst, although it loads properly, won't let me click on anything.

I can use the spacebar to get past the two intro screens but as soon as I get to the Book at the opening the game won't let me click on anything. I can't even click on any Options in the Esc menu.

Supposing your OS is Windows 7 or newer, I strongly suggest you to right-click on the shortcut you use to launch the game, and edit its compatibility settings as follow:
- XP compatibility (SP2) (or other, if you still have issues)
- Disable visual themes (Optional)
- Disable desktop composition (Optional)
- Run as Admin (Optional)

Try different combinations of the above.

These suggestions apply to both your games, meaning you can try them with both realMyst and Riven.

RealMyst worked on Compatibility.

I've been running Riven as Admin and have tried all the different Compatibility settings. It refuses to even show up as an Icon on the Toolbar. Everything should be running perfectly fine and I've tried to re-download it once already.

We still don't know your OS and PC specifics. It's hard to help you this way.