all explorer is is a GUI and doesnt have anything really important to the stability of windows so its safe to shut it off.
I'd disagree. For instance, its the only mainstream program I can think of that launches one of two completely different programs depending upon how many copies of itself are running when it launches (first explorer process creates the startbar and desktop, but no filesystem browser; all subsequents create filesystem browsers but no desktop etc).
Aside from that, IIRC it *is* possible to replace start bar etc - modulo the security system on windows that e.g. traps ctrl-alt-del - you just have to make sure explorer is not loaded (and isnt periodically re-launched by the OS - IIRC some versions of win2k and XP do this). Google for "alternative windows shell" and you should find many projects doing it, with interesting info, to varying degrees.