1. Go to your Start menu, click on Run and open up your Registry Editor by typing “regedit” without the quotes and press OK.
2. Once there go to: HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionExplorerAdvancedFolderHiddenSHOWALL
3. Delete the value CheckedValue. (Its type should be REG_SZ and data should be 0 or 1.)
4. Create a new DWORD value called CheckedValue (same as above, except that the type is REG_DWORD) by right clicking on the right pane->New->DWORD Value. Modify the value data to 1 (0x00000001).
Voila….