Using C#.NET in Excel 2003

Question

I created a new document in Excel project through C#. But when I started that project straight a way (means I added nothing in that code which was created by .NET). I encountered errors on the third & the fourth line i.e using Excel = Microsoft.Office.Interop.Excel; using MSForms = Microsoft.Vbe.Interop.Forms; Remember above lines is created by .NET. So how can I remove that error. is it the problem of installation??