I used 7zip to make the files which might be why xp can't uncompress them. As for the prefs.prop it should work for either the demo or the full episode. Should being the key word there.
"No man can be a pure specialist, without being in a strict sense, an idiot."
- George Bernard Shaw
"Remember, every time a April Fools joke is played, a point-n-click adventure game concept is killed."