Bzeitham wrote:
If the key is all the way in the lock cylinder and has lifted the tumblers (pins) you should be able to turn the cylinder with a small screwdriver inserting it into the cylinder and twisting. After unlocking in you might be able to remove the entire lock. Most hardware stores should have a lock that will replace yours. But check to see if you can possibly push the key from the back side of the lock. I own a hardware store and handle the lock rekeying. If you get the old key piece out take it to the hardware store and they should be able to copy the key.
GOOD LUCK!
I agree with the first sentence of this post, or try
How to remove a broken key that Pangaea Ron linked too. JMO