Actually, it might not be too bad.

Select columns B:C, then rightclick on the selection and choose Insert

Now select E:F and hit F4 (repeat last action)

But you could use a macro, too:

Option Explicit
Sub testme()
   Dim iCol As Long    
   With Worksheets("sheet1")
       For iCol = .Cells(1, .Columns.Count).End(xlToLeft).Column To 2 Step -1
           .Columns(iCol).Resize(, 2).Insert
       Next iCol
   End With
End Sub

I used row 1 to find the last used column.

If you're new to macros, you may want to read David McRitchie's intro at:
http://www.mvps.org/dmcritchie/excel/getstarted.htm