On the title screen press the 'SPACE BAR' to enter the music menu, then press '1', '4', '2', and then press 'ESC' twice. This should give you unlimited lives.
Another source gives these instructions:
Press 'Help' to get into the music menu, press '4' to turn off the music, then press '2'. After about 10 seconds of music, press 'Esc' twice. You can now start the game with infinite lives and power lines.