I just purchased a 2004 Honda Civic. I left the interior lights on over night and in the morning my car would initially not start. After a few tries I got my car to crank but now on the dashboard there is a light on. It's a green key that flashes whenever I'm driving. What is the flashing "key" for and how do I make it go away? Thanks.

The flashing green key is the immobilizer indicator light. It flashes continually when an unrecognized key is used. If it is flashing then your engine should not be running. Very interesting - I would try to disconnect the battery and hook it back up. If that doesn't work, you may need to go to a dealer so they can look use the scan tool on the immobilizer system.