I found yet another Windows tip I did not know in Richard Birkby's Explorer column handler shell extension in C# article at The Code Project:
Finally, if you want to restart an instance of Windows Explorer, you should use the official way to shut down Explorer, rather than killing it from Task Manager! To shut down officially, hit Start->Shutdown (or Turn Off Computer on Windows XP), then while holding the control shift and alt keys, click cancel on the shutdown dialog. To start a new instance of Windows Explorer, bring up Task Manager by holding the control and shift keys, then hit escape. In Task Manager, choose File->New Task and enter "Explorer.exe". This will have restarted Windows Explorer properly.