How to drop voltage output from 5V to 4V?

im modding my laptops cooling pad and rigging it up with leds, my problem is that the LEDs drop the voltage 2 volts(exactly) and the output of USB ports is 5Vs, so how can i drop the 5v power to 4Vs, basically because i might sell the pad and i dont want the new owner to be required to change any settings on there computer or anything :). THANKS A BUNCH!