ASP XMLHTTP Download timeout help!!

I have been using an ASP page to retrieve files from other websites and send them to my clients. The script is as following:
<%
URL=Request.Querystring("URL")

Response.Buffer = True
Dim objXMLHTTP, xml

Set xml = Server.CreateObject("Microsoft.XMLHTTP")

xml.Open "GET", URL, False
For FNC=1 to len(URL)
If mid(URL,FNC,1)="/" Then
STN=FNC
ElseIf mid(URL,FNC,1)="\" Then
STN=FNC
End If
Next

xml.Send 'This line takes too long for big files

FN=mid(URL,STN+1,len(URL)-STN)
FND = "attachment;filename=" & FN

' Add a header to give it a file name:
Response.AddHeader "Content-Disposition", FND

' Specify the content type to tell the browser what to do:
Response.ContentType = "application/zip"

' Binarywrite the bytes to the browser
Response.BinaryWrite xml.responseBody
URL=""
Set xml = Nothing
End If
%>



Now, the script works by loading the entire requested file into the buffer on the server, and then send the buffer's content to the client.
the script works fine on small files but when dealing with bigger files, there are two problems.
Firstly, the buffer might not be big enough to hold a file of for example 40MB, which causes error. And secondly(the problem that I am having now) the problem is that for slightly bigger files, although the buffer can hold the whole file, the command: xml.send takes too long to retrieve the file into the buffer before the asp page can give responses. this causes an error in the Internet broswer saying "connection timeout"


Is there anyone knows anyway I can make the data transfer "on the fly" or may be just stop the client's broswer saying "Connection Timeout"?