To add to Dai's post, Safe Mode allows the computer to boot up to the Windows Desktop without launching the system tray. That means you won't get your audio, graphics drivers, automatic updates, printer function to work in this mode.
Safe mode will tell you if you have virus issues, but more importantly if the display remains inverted chances are you have a display adapter driver issue and you will probably have to reinstall that driver.
Before going into safe mode go to your device manager and see if your display adapter is configured correctly. If there is a yellow exclamation mark or question mark next to it's listing, your display adapter driver is either corrupted or not installed and you are running your graphics under a Windows legacy driver (generic display driver that isn't compatible with your display).
But more than likely it's probably that driver that needs to be reinstalled.