Some months back I found a version of Linux called Zorin OS that has a range of alternate GUIs that look like Win 2000, Win XP, Win Vista, Win 7, Mac OS and others. It's based on Ubuntu and uses the Ubuntu repositories etc, just have some alternate GUI overlays. I've had people look at my system and ask how come I'm still running Win 2000 as it's that close to what they remember of the Win Classic desktop.