Hi,
Have you made any changes to the computer prior to the issue?
Method 1: Run hardware and device troubleshooter and check if it fixes the issue:
http://windows.microsoft.com/en-US/windows7/Open-the-Hardware-and-Devices-troubleshooter
Method 2: You can also reset the USB controller and check if it makes any difference:
a) Type devmgmt.msc in start search box.
b) Expand Universal Serial Bus controllers.
c) Right-click every device under the Universal Serial Bus controllers node, and then click Uninstall to remove them one at a time.
d) Restart the computer, and then reinstall the USB controllers.
e) Plug in the removable USB storage device, and then test to make sure that the issue is resolved.