With the disk assumed in the tray and the tray closed:
For PS2 games, power up normally from STANDBY with RESET button.
A single tap is required.
For PS1 games & DVD Movies, power up from STANDBY with RESET button held until the blue EJECT light comes on; then release RESET and the disk will boot.
Please turn off the PS2 (to standby) before changing Mode (PS1/PS2/DVD)
Hope that helps....