Error opening excel file with VB (error with office DLL)

  

Can not convert COM object of type   'Microsoft.Office.Interop.Excel2000.ApplicationClass' to the type of   interface 'Microsoft.Office.Interop.Excel2000._Application'.
  There was a   operation error because the QueryInterface call in the   COM component for the interface with IID   '{000208D5-0000-0000-C000-000000000046}' generated the following error:
  Error loading the type / DLL library. (Exception from HRESULT:   0x80029C4A (TYPE_E_CANTLOADLIBRARY)).

Any ideas?

Thanks!