Hi,
· Do you see any yellow bang in the device manager?
· What happens exactly when you try to open the hard drive?
I would suggest you to follow these steps and check if the issue is fixed.
a) Open Device Manager by clicking the Start button, clicking Control Panel, clicking System and Security, and then, under System, clicking Device Manager. If you're prompted for an administrator password or confirmation, type the password or provide confirmation.
b) In the list of hardware categories, find the device, and then double-click the device name.
**c)**Click the Driver tab, click Uninstall Driver.
d) Restart the computer, let Windows find drivers automatically.
You may also run Check disk to check for errors in external hard drive. Follow the instructions in the below mentioned link.
Check a drive for errors:
http://windows.microsoft.com/en-us/windows7/Check-a-drive-for-errors
Come back and let us know the status.
Thanks and regards,
Bikesh Thakur
Microsoft Answers Support Engineer. Visit our Microsoft Answers Feedback Forum and let us know what you think.