Click on "Start" -->Run-->type cmd and click on OK. Here I assume your external hard drive as G:
Enter the following command.
attrib -h -r -s /s /d g:\*.*
ou can copy the above command --> Right-click in the Command Prompt and paste it.
Note : Don't forget to replace the letter g with your external hard drive letter.
Now press "Enter".
Open Folder Options by clicking the Start button. , clicking Control Panel, clicking Appearance and Personalization, and then clicking Folder Options.
Click the View tab.
Under Advanced settings, click Show hidden files, folders, and drives, and then click OK.