IIS 7 & W2K8 - Access to path \\remotewinXP\folder\ is denied. No error on IIS 6 & W2K3 hosting. Any suggestion?

Hi,
Appreciate if someone could point to the right answer on how to overcome this error. By clicking the Button3, the ExportedFilePDF.pdf should be copied to the \\presario remote machine. So far, no security issue on the same configuration in IIS6 + W2K3.

  Protected Sub Button3_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button3.Click
        Try
            File.Copy("C:\BackOffice\Export\ExportedFilePDF.pdf", "\\presario\FaxServer\Outbox\ExportedFilePDF.pdf", True)
        Catch ex As Exception
            Response.Write("Error copying file | " & ex.ToString)
        End Try

    End Sub
 The browser will generate t ...