Okay okay..
Don't use a screwdriver unless you want to pinch your tube.
If you start at the valve and push the tyre around you gain a little bit of slack at the opposite site of the wheel.
At the opposite side, HTFU and break your thumbs to push the tyre off the rim.
Easy peasy
This has been covered already so I'm not going to add anything useful..
http://www.youtube.com/watch?v=unkIVvjZc9Y
Okay okay..
Don't use a screwdriver unless you want to pinch your tube.
If you start at the valve and push the tyre around you gain a little bit of slack at the opposite site of the wheel.
At the opposite side, HTFU and break your thumbs to push the tyre off the rim.
Easy peasy