I have hp pavilion dv9608 notebook pc how to download a dvd disc?

By "download" are you asking how to download a DVD over the Internet? You can watch movies using streaming video or you can download and save them to disk but you need DVD software to do that. I'm not sure what that model notebook's capabilities are but here's the link for support for that product:

http://h10025.www1.hp.com/ewfrf/wc/product?cc=us&lc=en&dlc=en&product=3548476