I found the steps to do this in this thread (posted by dentrecords):
Why is my A/C always on?
1. Turn car on.
2. Turn temperature knob all the way cold and turn the fan knob to off.
3. Put vent location to "face"
4. Turn car off
5. Hold down the Recirculation Button and the A/C Button.
6. Hold down both buttons and turn the key all the way to the on position.
7. Keep both buttons depressed until one of the lights blink a few times, then you get a solid green light once the change has been made. Then let go.
8. See if it works by putting the fan on in Defrost. You should see the A/C light turn on and you should be able to turn it off.
The steps worked like a charm. I can now defrost my frozen windows without waisting money (and slowing things down) with AC.