About your query/statement in shoutbox regarding YouTube not downloading videos untill fully played ...
I dont know if you are a new user to IDM or not, but to my experience, When you click the download button of IDM, you HAVE to stop the VIDEO, not by pausing it, but by either closing down the window, or by right clicking on the Video and select "stop download"
If you let the video continue steam, while you already have clicked on IDM's download button, IDM won't download the video untill they are fully streamed. But in this case you have an Advantage, that IDM will not download the video AGAIN. It'll only SAVE the ALREADY STREAMED video.