There are more ways than one to kill Windows Explorer in both Windows Vista and Windows XP. The fact of the matter is that, in some scenarios, stopping Explorer.exe is a viable alternative to restarting the entire operating system. Some changes associated with registry modifications and even programs you install require a system reboot. Sometime, just sometime you will be able to get away with it just by restarting Windows Explorer and not the entire operating system.
Now, the most common way to shut down Explorer.exe is through the Task Manager. Press Ctrl + Alt + Del or Ctrl + Alt + Esc in both Vista and XP and you will open the Task Manager. Here, make your way to the Processes tab and locate Explorer.exe, select it and hit End process. The immediate result of such an action is that the main Windows Explorer process will be shut down. Alternatively you could of course use Process Explorer in order to close Explorer.exe.
However, End Process will completely terminate Windows Explorer leaving you out to dry, and sometime generating some adjacent issues. Fortunately, both Windows XP and Windows Vista feature alternative, healthy approaches to shutting down Windows Explorer. In XP make your way via the Start Menu, then Turn Off Computer and just press Ctrl + Alt + Shift and click on the cancel button of the shut down dialog box.
In Windows Vista, the process has been simplified. All you have to do is open the Start Menu, hold Ctrl and Shift pressed down and right click on the empty surface in the menu. A contextual menu will be displayed containing two options: Properties and Exit Explorer. I think you will be able to take it from here...
"Note that on both Windows XP and Windows Vista, only the "main" Explorer process exits – that is, the process that manages the Start menu, taskbar, and desktop. With default settings, all Explorer folder windows are managed by that process as well, and so they will close too. However, if you have configured Explorer to "launch folder windows in a separate process", then those folder windows will not close when you apply this trick. Furthermore, when I tried this on Windows XP, I needed to manually close all those folder windows before running a new instance of Explorer would display the taskbar, etc., instead of just displaying yet another folder window. Why is this hidden nugget even there? Its purpose is to help developers and testers who work on shell extensions to be able to stop and restart Explorer quickly and cleanly without having to log out," revealed Aaron Margosis, Senior Consultant, Microsoft Consulting Services.
In order to open up Windows Explorer again you will have to resort to Task Manager, since Run will be inaccessible through the Windows key + R combination. In the Task Manager, under File, choose New Task (Run...), enter "explorer" in the dialog box and hit Enter.
Microsoft, Windows Vista, Windows Explorer, Tips and Tricks, Knowledgebase