I don't actually have windows 7, (windows XP is what i run) but when I wanted to install those games on my system, i just put in the disk and followed the onscreen prompts to install. Occassionally I had trouble with running Myst because it needs to run in 256 colour mode, but i just had to save, shut the game off, and load it again and it was fine. Riven gave me no trouble at all.
Have you tried just installing them and running them from the CD's? Again, i have no experience with windows 7, so maybe that won't work. Sorry I can't be more help :/