http://www.associatedcontent.com/article/279786/how_to_remove_a_parking_boot.html?page=3&cat=27
"Removing the boot without tools or damage is actually a very simple matter. Simply let out about half of the air from the "booted" tired. Once you let the air out the prong that holds the boot in place can be slid past the tire, exposing the hubcap. I had initially intended to change the tire but I found that after sliding the clamp off the front of the tire the rest of the boot was only hooked into the wheel from the rear. I got behind the wheel of the car, started it and drove it a few inches forward and the torque of the wheel immediately popped the boot completely off."