下载 可以用流下载(耗内存，少用)或直接转到该文件.

<%

ConstUSE_STREAM=0'0.不用流(Adodb.Stream)下载1.用流下载
ConstALLOW_FILE_EXT="rar,zip,chm,doc,xls,swf,mp3,gif,jpg,jpeg,png,bmp"'允许下载的文件的扩展名，防止源代码被下载

DimsDownFilePath'下载文件路径
sDownFilePath=Trim(Request("FilePath"))
'或者根据传过来的文件ID从数据库中获取文件路径

'如果sDownFilePath为绝对路径，一定要将sDownFilePath转换为相对本文件的相对路径

'sDownFilePath="focus.swf"

CallDownloadFile(sDownFilePath)

FunctionDownloadFile(s_DownFilePath)
   '判断有没传递文件名
   IfIsNull(s_DownFilePath)=TrueOrTrim(s_DownFilePath)=""Then
       OutputErr"错误：先确定要下载的文件，下载失败"
   EndIf

   '判断扩展名是否合法
   Dims_FileExt
   s_FileExt=Mid(s_DownFilePath,InstrRev(s_DownFilePath,".")+1)
   IfInStr(","&ALLOW_FILE_EXT&",",","&s_FileExt&",")<=0Then
       OutputErr"错误：文件类型（"&s_FileExt&"）不允许被下载，下载失败"
   EndIf
   
   s_DownFilePath=Replace(s_DownFilePath,"","/")

   '为了安全，某些目录禁止下载文件，在这里处理
   '
   
   '检测服务器是否支持fso
   Dimo_Fso
   OnErrorResumeNext
   Seto_Fso=Server.CreateObject("Scripting.FileSystemObject")
   IfErr.Number<>0Then
       Err.Clear
       OutputErr"错误：服务器不支持fso组件，下载失败"
   EndIf

   '取得文件名，文件大小
   Dims_FileMapPath
   Dimo_File,s_FileName,n_FileLength
   s_FileMapPath=Server.MapPath(s_DownFilePath)
   If(o_Fso.FileExists(s_FileMapPath))=TrueThen
       Seto_File=o_Fso.GetFile(s_FileMapPath)
       s_FileName=o_File.Name
       n_FileLength=o_File.Size
       o_File.Close
   Else
       OutputErr"错误：文件不存在，下载失败"
   EndIf
   Seto_Fso=Nothing

   '判断是否下载的文件大小超过限制
   '   
   
   '如果不是用流下载，直接转到该文件
   IfUSE_STREAM=0Then
       Response.RedirectsDownFilePath
       Response.end
   EndIf

   '检测服务器是否支持Adodb.Stream
   OnErrorResumeNext
   Seto_Stream=Server.CreateObject("Adodb.Stream")
   IfErr.Number<>0Then
       Err.Clear
       OutputErr"错误：服务器不支持Adodb.Stream组件，下载失败"
   EndIf

   o_Stream.Tyep=1
   o_Stream.Open
   o_Stream.LoadFromFiles_FileMapPath

   Response.Buffer=True
   Response.Clear
   Response.AddHeader"Content-Disposition","attachment;filename="&s_FileName
   Response.AddHeader"Content-Length",n_FileLength
   Response.CharSet="UTF-8"
   Response.ContentType="application/octet-stream"
   Response.BinaryWriteo_Stream.Read
   Response.Flush

   o_Stream.Close
   Seto_Stream=Nothing

EndFunction

SubOutputErr(s_ErrMsg)
   Response.Write"<fontcolor=red>"&s_ErrMsg&"</font>"
   Response.End
EndSub

%>

http://www.cnblogs.com/jiny-z/archive/2006/08/29/489102.html