This will show you how to change the Windows 7 pinned Windows Explorer taskbar icon from the default Open To the Libraries window target to Open To the Computer window target when you click on the Windows Explorer icon on the taskbar.

1. Right-click on the pinned Windows Explorer taskbar icon, then right-click on Windows Explorer in the Jump List.
2. Click on Properties.
3. On the "Shortcut" tab, make sure the field box to the right of "Start in" is empty.
4. In the "Target:" field, the default is %windir%\explorer.exe.  Change the default to:
   %windir%\explorer.exe /n,::{20D04FE0-3AEA-1069-A2D8-08002B30309D}
5. Click OK to save the changes.

Now, when you click the taskbar icon, Windows Explorer should open and display all of your local and network drives instead of displaying your Libraries.