Have you encountered enabling your hidden files but doesn’t work?  Reason is, you have been infected by a virus called “RAVMON”. Not only this virus can disable your “Show Hidden Files and Folders” but can disable also your Task Manager, Registry Editor and Command prompt.

So heres a quick solution on how to enable it again:
1. Go to START menu

2. Click RUN

3. Type in the keyword regedit and press ok

4. The Registry window will pop-out now locate this folders:
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced\Folder\Hidden\SHOWALL

5. Find a key called checkedValue (0)

6. Change the Value of checkedValue to (1) then click OK.