When I perform a warm boot, I have no problems booting up. But after leaving the machine shut down over night, in the morning it only gets as far as the splash screen and then stops. I have restarted and tried to load windows in DOS, but I get an error saying that HIMEM is missing. I have reinstalled windows and this seems to work. But after shutting it down overnight, the same problem occurs again. Any ideas on what may be the problem?