You do not need software to use your phone as a regular fixed, wired phone. By connecting it to the back of your modem, you are simply adding a phone to the phone line connected to your computer. No software, or configurations necessary.
The phone patch in XP pro will allow you to soft-dial, but necessary basic features such as on-hook/off-hook, flash, etc. cannot be controlled by software if using a normal phone. (Unless you have a fully-controllable voice modem, but then you wouldn't need an external fixed phone!).