I have already done that still its giving error for files say larger than 15MB.

Error:  "Unable to find the uploaded file in directory : C:\inetpub\wwwroot\TestDragDropUpload\Uploads "

Smaller files are uploading without error and are avaliable in specified upload folder.

I have set in web.config - for large file upload -

<system.web>
      <httpRuntime maxRequestLength="1000000" executionTimeout="10800"/>
    </system.web>
    <system.webServer>
      <security>
        <requestFiltering>
          <requestLimits maxAllowedContentLength="1073741824"/>
        </requestFiltering>
      </security>
    </system.webServer>

 Please help.