Thank you RahRah. I'll try

It turns out the version of Myst that I've been playing IS the Myst Masterpiece Edition.

Since I'm playing the game via Steam, I haven't figured out how to run it as an administrator. Right-clicking on the icon and then on "Properties" brings up the game as a web document URL.

I can go to the Security tab and change Permissions to let the Administrator run it instead of the System.

I am trembling in terror at the very idea, though. What if something goes wrong and I can't switch back? Is it worth the risk?

I could end up blowing up Steam singlehandedly. Well, the small portion of it that lives on my computer.

I think I need someone to hold my hand.