usb stick says the disk is write protected

First look for a tiny lock switch on the side. Most plain sticks don't have one, but SD cards in an adapter and some branded drives do. No switch? Open cmd as admin, run diskpart, then list disk, select disk N (the stick - check the size so you don't pick your main drive), then attributes disk clear readonly. If that doesn't stick either, bad news: cheap flash drives lock themselves read-only when the memory starts failing, as a last protection for your data. Copy everything off while it still reads and replace it.