how to stream file

How can I properly stream file in ASP? The user would be clicking through a link which call a asp page with a url encode of the filename. The link looks like this:
http://../files.asp?f=D%3A%5CSandBoxes%5CEPZ%Support+Tech%5Croot%5Cdownloads%5CNew+Winamp+media+file%2Ewav&e=ephz@mail.com

And here's the codes for files.asp:


<%

Dim email, filename, dFiles,  msg
Dim strSQL
filename=request("f")
email = Request("e")

strSQL = "SELECT * FROM EmailDownloads WHERE email = '" & email "' AND filename = '" & filename & "'"
rs.Open strSQL, objConn, adOpenKeyset, adLockPessimistic

If Not rs.EOF Then

dim objFSO, objTS
Set objFSO = Server.CreateObject("Scripting.FileSystemObject")
Set objTS = objFSO.OpenTextFile(fileName)

sFileType= Right(fileName,4)

Select Case sFileType
            Case ".asf"
                sContentType = "video/x-ms-asf"
            Case ".avi"
                sContentType = "video/avi"
            Case ".doc"
                sContentType = "application/msword"
            Case ".zip"
                sContentType = "application/zip"
         Case ".css"
                sContentType = "text/css"
      Case ".pdf"
                sContentType = "application/pdf"
            Case ".xls"
                sContentType = "application/vnd.ms-excel"
            Case ".gif"
                sContentType = "image/gif"
            Case ".jpg", "jpeg"
                sContentType = "image/jpeg"
            Case ".wav"
                sContentType = "audio/wav"
            Case ".mp3"
                sContentType = "audio/mpeg3"
            Case ".mpg", "mpeg"
                sContentType = "video/mpeg"
            Case ".rtf"
                sContentType = "application/rtf"
         Case ".htm", "html"
                sContentType = "text/html"
         Case ".asp", ".asa"
                sContentType = "text/asp"
            Case Else
                sContentType = "application/x-msdownload"
End Select

NameFile=Right(FileName,Len(FileName)-InstrRev(FileName,"\"))

Response.ContentType = sContentType
response.AddHeader "Content-Disposition", "attachment;filename=" & NameFile

    Response.Buffer = True
    Do While Not objTS.AtEndOfStream
      strChunk = objTS.Read(32)
      strTmp = ""
      For i = 1 to Len(strChunk)
           strTmp = strTmp & ChrB(Asc(Mid(strChunk, i, 1)))
      Next
      Response.BinaryWrite strTmp
      Response.Flush
    Loop
    objTS.Close
    Set objTS = Nothing
    Set objFSO = Nothing

Else
Response.Redirect "login/login.asp"
Response.End
End If

%>

Problem:
How to decode the url encode string?
The file is stored locally on the server directory.  As you can see I also used Server.MapPath for the file location. Is this the correct way to stream file content in ASP?

Thanks!