(I've come across USB drives that work on Windows without special drivers, but not on Linux or OS X.) S.M.A.R.T. In the latter case, a different operating system is worth a try. In the a former case, with a bit of luck, a data recovery specialist with an appropriately equipped lab can salvage its content. If this command results in a message about an “Input/output error”, our drive is broken or otherwise fails to interact with the Linux kernel as expected.
This can be verified easily with: sudo dd if=/dev/sdc of=/dev/null count=1 It still appears as a block device to the kernel and in the disk manager, but its first sector holding the partition table is not readable. Sometimes a storage medium simply refuses to work at all.