Restoring to factory settings

My fault, I should have said my PC is picking the USB drive up fine. I can put files onto it. My Pioneer programme is no longer picking it up and neither is my Pioneer decks. I bought this USB stick for my Pioneer decks only. I must have removed a factory file from the Sandisk that worked with my Pioneer. I will buy another one and pinch all the files from that, and put those on my old Sandisk. I think I will try formatting it again, I only done a quick formatt last time. I will do a full one. Thanks