VS 2005 Save File On Button Click

I have written a script to create txt documents on my server and i have a listbox on my aspx page that lists these txt documents 1 by 1. What i want to do is click a button to let the user save the selected file to there own computer... sounds simple but im having a mare.

Heres my code:
Code:
Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
'Server.Transfer(MapPath("/") & ListBox1.SelectedValue)
DownloadFile(ListBox1.SelectedValue, True)
End Sub
Private Sub DownloadFile(ByVal fname As String, ByVal forceDownload As Boolean)
Dim path__1 As String = MapPath(fname)
Dim name As String = Path.GetFileName(path__1)
Dim ext As String = Path.GetExtension(path__1)
Dim type As String = ""
' set known types based on file extension
If ext IsNot Nothing Then
Select Case ext.ToLower()
Case ".htm", ".html"
type = "text/HTML"
Exit Select
Case ".txt"
type = "text/plain"
Exit Select
Case ".doc", ".rtf"
type = "Application/msword"
Exit Select
End Select
End If
If forceDownload Then
Response.AppendHeader("content-disposition", "attachment; filename=" & name)
End If
If type <> "" Then
Response.ContentType = type
End If
Response.WriteFile(path__1)
Response.[End]()
End Sub
Here's the error message i get:

Code:

Access to the path 'C:xml' is denied. Permissions is the obvious but i cannot go around changing the permissions on all my end users PC... there must be an easier way?