XP to Win 7

Since my PC was seven years old, I decided to buy a new one (Picked it up today!
). On my old XP machine I was running all of my Myst games from an external hard drive. I've attached this drive to my new PC running Windows 7 and tried running Uru from it without re-installing it through Windows 7. It works but with problems. It's only letting me run in 800x600 and it gives me the message, "This program might not be installed correctly." Should I attempt to use the re-install option that pops up with this message or should I simply re-install from scratch. I ask because I currently have 14 installations of Uru on this external drive including various shards and custom offline installations.
I really don't want to try to re-create all of these. Is there a way to "fix" all 14 without starting over?

