You can try to repair your Office 2010. This may require your dvd and product code.
You could try the following macro:
Code:
Sub NavPaneshow()
Application.CommandBars("Navigation").Position = msoBarLeft
Application.CommandBars("Navigation").Visible = True
End Sub
Instructions for Installing Macros from Forums or Websites by Graham Mayor, MVP
Install/Employ VBA Procedures (Macros) by Greg Maxey, MVP