Win Me shutdown problems

When shutting down Win Me properly from the start menu, after selecting “shutdown” computer proceeds to shutdown, screen flickers then shows brown vertical lines across screen which remain. At that point computer won’t respond when attempting to complete power down or attempting power up. After holding down power button for 5 secs system will start but runs scandisk because of improper power down. System is an off the shelf HP 700 Mhz running Win Me and basic software. Adjusting Power management settings doesn’t seem to help. Any ideas?