I used to live on YouTube for some of my learning & research. I'm looking for a way other than the offline playback feature provided by YouTube in which I can search and play videos, and when I play a video it automatically gets downloaded on my hard drive in my chosen video format. Is there any application available for my need? I'm on Windows 7.
It doesn't fully meet your requirement, but you can try flashgot for firefox, it gives a download media button whenever media is playing for any format which the site offers.
Disclaimer: Downloading youtube videos may be against Google's TOS, so do your own legal research.