The following will alter your game files. It is highly suggested that you make a back-up copy of your files before you alter them beyond all recognition.

You can unlock all the cars and tracks by reducing the price of locked cars/tracks to either 0 or a very low value. To do this, simply use notepad to edit the cars.ini file in the following directory:

C:\Program Files\EA Games\Need For Speed Hot Pursuit 2\Edit Cars\

You can do the same for the Tracks.ini file in the directory

C:\Program Files\EA Games\Need For Speed Hot Pursuit 2\Edit Cars\tracks\

When you reload the game you can see the results.