If you are running an old version of Ubuntu (9.xx?) then you should try upgrading.
If you are on Ubuntu 10.04 and up, go the System>Preferences>Keyboard Shortcuts, and add new short cuts for your multimedia keys (they will almost definitely be detected). In fact, they may already exist, but not be assigned to launch any applications.
As for the volume/play/pause/stop buttons (I believe you have those, if it is a dv2000) you should be able to use those out of the box in most recent versions of Ubuntu (even most older versions). If you are not able to use those buttons in particular, then you should report a bug (but only if you are using a supported version of Ubuntu; which means 10.04 and up).
If you are not sure they are being detected, run
xev in a terminal and press the keys. You will see their key codes on the terminal if they are working. If you don't, then something is wrong with your system either physically or in the software.
There is a program that might help you (though I no longer have it installed, and thus can no longer provide screenshots).
It is called Keytouch-editor, and it helped me in the past with a similar issue (since then Ubuntu supports my QuickPlay button and all the other buttons just fine). Install Keytouch-editor is pretty straight forward and you should be able to learn it quickly.
You can find it in the software center, or install it from the command line with
sudo apt-get install keytouch-editor.
Once you have it installed, and have run it, you can assign your Quickplay buttons to launch the media programs (or anything else for that matter) of your choice. Keytouch-editor makes it very simple.