USB drives can be Handy. They can backup your files, allow you to physically move files, and even run an OS. However, when buying them online (especially places like eBay) it is possible to run into a hacked USB drive. For example: A 256MB thumb drive is hacked to say it has 8Gig. When plugged into a computer it shows 8Gig of free space, but when your computer writes beyond 256MB things begin to be corrupted. Be sure to check the reviews and use a tool like H2testw before relying on a thumb drive. If all else fails you request a refund from Ebay or Paypal (if either of those were part of the transaction).