可以用流下载(耗内存，少用)或直接转到该文件.

<%

const use_stream = 0 0.不用流(adodb.stream)下载 1.用流下载
const allow_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

dim sdownfilepath 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"

call downloadfile(sdownfilepath)

function downloadfile(s_downfilepath)
    判断有没传递文件名
    if isnull(s_downfilepath) = true or trim(s_downfilepath) = "" then
        outputerr "错误：先确定要下载的文件，下载失败"
    end if

    判断扩展名是否合法
    dim s_fileext
    s_fileext = mid(s_downfilepath, instrrev(s_downfilepath, ".")+1)
    if instr("," & allow_file_ext & ",", "," & s_fileext & ",") <= 0 then
        outputerr "错误：文件类型（" & s_fileext & "）不允许被下载，下载失败"
    end if
   
    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
    dim o_fso
    on error resume next
    set o_fso = server.createobject("scripting.filesystemobject")
    if err.number <> 0 then
        err.clear
        outputerr "错误：服务器不支持fso组件，下载失败"
    end if

    取得文件名，文件大小
    dim s_filemappath
    dim o_file, s_filename, n_filelength
    s_filemappath = server.mappath(s_downfilepath)
    if (o_fso.fileexists(s_filemappath)) = true then
        set o_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"
    end if
    set o_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
    if use_stream = 0 then
        response.redirect sdownfilepath
        response.end
    end if

    检测服务器是否支持adodb.stream
    on error resume next
    set o_stream = server.createobject("adodb.stream")
    if err.number <> 0 then
        err.clear
        outputerr "错误：服务器不支持adodb.stream组件，下载失败"
    end if

    o_stream.tyep = 1
    o_stream.open
    o_stream.loadfromfile s_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.binarywrite o_stream.read
    response.flush

    o_stream.close
    set o_stream = nothing

end function

sub outputerr(s_errmsg)
    response.write "<font color=red>" & s_errmsg & "</font>"
    response.end
end sub

%>