The screw that holds down the string retainer on a Jazz Bass that I recently picked up is stripped. The retainer flops around a bit and I would like to tighten it down. The head of the screw is so badly damaged, I can't get a screwdriver to engage to tighten or loosen the screw.

Any suggestions on how to get this thing out? It is in a pretty inaccessible spot and I have exhausted everything I can think of.

drill it out a bit and use an easy out, or more comonly called a "spiral screw extractor"

take a file or a dremel and make a new slot in the top