Sometimes you want a user to download a binary file instead of opening it inside the browser window.
There are several different ways to accomplish this.
Generically:

<%
FileName = "Document.Doc"
Response.ContentType = "application/octet-stream"
Response.AddHeader "content-disposition", "attachment; filename =" & filename
Set Stream = Server.CreateObject("ADODB.Stream")
Stream.Open
Stream.LoadFromFile Server.MapPath(Filename)
Conents = Stream.ReadText
Response.BinaryWrite Contents
Stream.Close
Set Stream = Nothing
%>

If you know the file type that you would like the user to download, try:
<%
Filename = "document.doc"
Response.ContentType = "application/vnd.ms-word"
Response.AddHeader "content-disposition", "attachment; filename=" & filename
%>

Other Content Types:
vnd.ms-excel - For Excel
vnd.ms-powerpoint - For PowerPoint
vnd.ms-project - For Microsoft Project
pdf - For Adobe Acrobat Documents
rtf - For Rick Text Documents
vnd.lotus-wordpro - For WordPro
vnd.lotus-1-2-3 - For Lotus 1-2-3
vnd.visio - For Visio
jpeg - for JPG Image File
gif - for GIF Image File
png - for PNG Image File