The Explorer process in Windows 7 handles the taskbar and any of the Explorer instances you create to browse directories. Due to file handles problems with applications, directories on plugged-in portable devices or on network share folders, Explorer might sometimes behave erratically. You might face one of these problems with Explorer:
Explorer hangs while displaying a directory or during a cut-copy-paste operation.
Explorer does not show up when its invoked by clicking its icon or by pressing the keyboard shortcut
Win + e.
Taskbar is frozen or has disappeared.
First, it is better to carefully kill all currently running Explorer instances. To do this open Task Manager. One way to do this is using the keyboard shortcut
Ctrl + Shift + Esc. In Task Manager, click the Processes tab, there should be one or more
explorer.exe instances. Right-click on each
explorer.exe and choose End Process. Do not choose End Process Tree! That would kill
explorer.exe and all the application processes it might have spawned, this is not good. End Process only kills
explorer.exe, making its children processes as orphans, but they are otherwise unharmed. All open Explorer windows and the Taskbar disappear after this operation.
Next, create a fresh new instance of Explorer. This can be done in Task Manager itself. Switch to the Applications tab and click New Task. Type in
explorer and click OK. Your taskbar should be back and hopefully you should be able to invoke Explorer without any problems after this.