This is a common error that occurs on Windows computers when the operating system cannot access the data on an external hard drive:

You might see this error after you try to open something from a USB drive. Or, depending on how your computer is set up, it might appear right after you insert the drive into your computer.

This "not accessible" error can occur at any time, even if you have recently used the drive. The location at the beginning of the error message is unique for each location that is unreadable, so it could be E:, H:, K:, etc.

There are several reasons why you might see this error: