When you click the Windows Explorer shortcut which is Pinned to the Taskbar, or when running explorer.exe directly in Windows 7, the following error message may be displayed with text "explorer.exe" in the title bar.
This file does not have a program associated with it for performing this action. Please install a program or, if one is already installed, create an association in the Default Programs control panel.
And using the WinKey + E key sequence causes "Unspecified error"
However, Windows Explorer may launch correctly when including additional switches such as /e or /n with explorer.exe, or double-click the (My) Computer icon. This problem occurs due to missing data in the "HKCR\Folders" registry key.