Prompt "Save As" Dialog For Image

I'm trying to force save as dialogue using this code in download.asp..but
when it runs it prompts for download.asp to save or open.

code snippet (from aspfaq.com)

Response.ContentType = "application/x-unknown" ' arbitrary
fn = "wallpaper_1_1.jpg"
Response.write "<br>" & Server.MapPath("wallpaper") & "<br>"
FPath = Server.MapPath("wallpaper") & fn
Response.AddHeader "Content-Disposition","attachment; filename=" & fn

Set adoStream = CreateObject("ADODB.Stream")
adoStream.Open()
adoStream.Type = 1
adoStream.LoadFromFile(FPath)
Response.BinaryWrite adoStream.Read()
adoStream.Close
Set adoStream = Nothing

I want this page to prompt save image option, not page itself.