Removing Shower Handles

I have a leaky bathtub faucet and am attempting to remove the handles. My hope is to replace the handle washers. The age of the faucets is 13 years. They have a screw in the middle. I can move the screw, but not completely - so I cannot disassemble the handle. Any suggestions?

You can take the stems to Low*s and see if they have a replacement stem you can buy. Also look inside the valve in the wall with a flashlight and look at the ring that the washer closes onto and be sure that there are no cuts in them. If there are you will need to replace them (seats). The new stems will not help if the seats are bad.