Store music? huh?
* go to one of a billion music playing websites
* Search for the track you want
* Click play
It depends what you mean by DVD. If you're talking about a physical DVD, then obviously no you can't. If you mean play the movie/tv show, then yes obviously you can.
Yeah, provided you have the bandwidth. If you don't, any OS has music management software.
> Play your video game online?
You got me there - not yet. Half life doesn't work in Flash.
> Type papers online? And no, google apps don't quite cut it :P
You can, but if you don't want to, any OS has productivity software.
> Watch a dvd online?
Yes.
> Do your taxes (in a Turbotax) fashion online?
Yes.