You'll want to get a rust/threadlock removal compound.is the spurgear metal? If No then make sure that you get one that will not harm plastic although it will probabaly not be as effective. Even letting some graphite or silicone based lubricant soak in for an hour or so might help. If worse comes to worse you may find yourself using an EZout. If the screw is already beaten up you will need to replace it anyway.