Has anyone had a Dell Latitude D600? Your experience is needed.

Mine has a battery that only lasts 30–40 minutes. That seems wrong, so I’m wondering what to do.
I’ve thought of installing a secondary battery, and also replacing the current one, or maybe doing both.

Mine is used, which I know may affect how long lasting it is, so how long does a new primary battery last? How long does a new secondary battery last? How long does a 4 cell battery last compared to a 6 cell or 9 cell battery?

Also, I know that what programs are running, the screen brightness, etc. are factors in how long the battery lasts, so no one should say “the answer depends on what you’re using the laptop for”. What I would prefer is for you to give specific examples of what you’ve used your Latitude D600 for and how long the battery has lasted under those circumstances.