Pendrive "lost boot signature"

69Rixter

I have a 4 Gb Sandisk pendrive that "lost boot signature". I cannot mount it, therefore cannot use any 'usual" methods to re-format or wipe or delete-reinstall a partition. What can I do to get this pendrive working again? Also, I have a 16Gb Sandisk pendrive that registers only 14.8Gb when completely empty? Is there a hidden 'trash" file and if so, how do I delete it? Otherwise, why is there almost 1 Gb 'hidden"?

Thank You:

Rick



ADDENDUM: Sandisk strictly uses the Gb format (1Gb=1024 Mb)therefore , do the math and you come up with only 14.8. Yes, it's a blatant ripoff/maketing ploy.