cant upload file because of file size in asp.net mvc 2?

i am trying to upload a file with filesize 80M bytes. on my pc ( cassini server) i can upload the file. On the webserver (iis 6) it throws an error?:

404 - File or directory not found. The resource you are looking for might have been removed, had its name changed, or is temporarily unavailable.

this is what i have i开发者_如何学Cn my web.config:

  <system.web><httpRuntime maxRequestLength="716800"/></system.web>

Try below configuration setting:

    <system.webServer>
        <security>
            <requestFiltering>
                <!-- 50 * 1024 * 1024 = 52428800 -->
                <requestLimits maxAllowedContentLength="52428800"/>
            </requestFiltering>
        </security>
    </system.webServer>