For Ross's comment about the Windows shell being embedded so far in the OS that it's a pain to mess around with/replace, there's some good-ish news. Microsoft have apparently finally decided to separate the Windows shell from the OS layer, which should hopefully mean that shell replacements become much easier to implement in the future. Their main reasoning is so that they can push out shell updates without needing a full OS update, but dummying it out and replacing it with a custom shell should become trivial. How long this will take though... that's yet to be seen. As a Windows developer myself, the shell is pretty deeply nestled in there.