When I came home today and logged on to my account, a message with the default user screen background saying "preparing desktop environment". When I got onto my Desktop all of the icons had been removed, my background replaced, and start menu, taskbar, and other personalized settings had been erased. After replacing everything again I logged out and came back on later and it had been all been replaced again. All of my files are still in my /users folder, but my desktop remains empty. I have windows 64 bit, if that helps. Thanks!