there is a way but it involves jamming a knife (or other object) into the tray mechanism of your machine and wiggling it about a bit, popping the tray out, swapping, forcing tray back in, wiggling that knife (or other object) about a bit more then crossing your fingers hoping that it has worked
not recommended unless you have money to burn and want to buy another PS2 in the near future
more cost efficient to purchase a modchip.
if you still want to wreck your machine try searching for "knife trick"