File download trouble

I have a file download link on my website that is not working. When a user tries to download the file, they get the following error:

http error 404-- File or Directory Not Found

The file is located in the proper directory, so I don't think that is the problem.

The following is the code for the download link page:

<%@ Page Language="C#" MasterPageFile="~/Marilyn.master" AutoEventWireup="true" CodeFile="DownloadNetwork.aspx.cs" Inherits="DownloadNetwork" %>

<%@ Register Src="Controls/NewsPanel.ascx" TagName="NewsPanel" TagPrefix="uc2" %>

<%@ Register Src="Controls/Balloon.ascx" TagName="Balloon" TagPrefix="uc3" %>

<asp:Content ID="Headers" ContentPlaceHolderID="Headers" Runat="Server">

<script type='text/javascript' language="javascript">

function onLoad(){

window.location='tmp/marilyn.xdsl';

}

script>

asp:Content>

<asp:Content ID="Content1" ContentPlaceHolderID="Main" Runat="Server">

<h1>Download the networkh1>

Your download should start automatically. <a href="tmp/marilyn.xdsl">Click herea> to download the network manually

<br /><br /><br /><br /><br /><br />

asp:Content>

<asp:Content ID="NewsPanel" ContentPlaceHolderID="Panel" Runat="Server">

<uc2:NewsPanel ID="NewsPanel2" runat="server" />

asp:Content>

Thanks!