Whenever I start the construction set, I get an error message that says I don't have a CD/DVD in my D: drive. I can just click continue and everything seems to work just fine, but it's a bit annoying. Putting any kind of disc in the D: drive solves this problem, but I bought the GOG version to get away from having to fiddle with CD's. It's by no means a dealbreaker or anything, but I figured I'd mention it.