Solve Windows 7 hanging upon boot when loading classpnp.sys

If your Windows 7 installation hangs upon boot with the Starting Windows icon, even with safe mode, here's what might fix it.  If the booting process stalls a bit on classpnp.sys in safe mode, try rebooting, going into the BIOS, and either resetting the BIOS to the factory default settings, or changing the HDD type to something different.  Then reboot either in Safe mode or normal mode, and hopefully you'll get the login screen.