You must add an entry for .id files in IIS. Open the Computer Management applet and open Properties on Internet Information Services.
Click on the "MIME Types" button. A window with a listing of MIME types will appear. Click on the "New..." button. Enter id for the extension, and a descriptive term for it such as "JUpload license file", as shown, and click OK.
You may need to restart IIS for these changes to take effect. You can verify that the file is now accessible, by entering the direct URL to the license.id file in your browser address bar.