Cheat Method
To purchase cars at a cheap price ($10 each), open up the cars.ini file in your CARS folder (from the main NFSHP2 game folder) using Notepad. Change the following lines:

price=10
nfsprice=10

NOTE: Always make a backup before overwriting game files.

Ferrari F50:
Lead a single race, full grid, advanced, for eight laps to unlock the NFS edition of the Ferrari F50.

Lamborgini Diablo 6.0 VT:
Get 2.5 million points to unlock the NFS edition of the Lamborghini Diablo.

McLaren F1:
Get 4 million points to unlock the NFS edition of the McLaren F1.

McLaren F1 LM:
Get 5 million points or win the World Championship to unlock the NFS edition of the McLaren F1 LM.

Mercedes CLK GTR:
Get 4.5 million points to unlock the NFS edition of the Mercedes CLK GTR.

Porsche Carrera GT:
Get 3.5 million points to unlock the NFS edition of the Porsche Carrera GT.

Dodge Viper GTS:
Get 2 million points to unlock the NFS edition of the Dodge Viper GTS.

Lamborghini Murcielago:
Get 3 million points to unlock the NFS edition of the Lamborghini Murcielago.

Faster cars:
Make a backup copy of the file before proceeding. Use a text editor to edit the "cars.ini" file in the "cars" sub-folder in the game directory. Change the "mass=" value to "100" for a faster car.

Open the folder of a powerful car, such as the F1, F50, etc. Copy the "car.ini" file from here and paste it over the original "car.ini" file of a slower car in its own folder (for example, the Elise). This instantly gives that car the speed and handling characteristics of the better vehicle. Note: Back up the original "car.ini" file of the slower car in the event that you want to revert it back to its standard settings.

Command-Line Parameters
Start the game using any of the following command-line parameters to activate the corresponding cheat. You can do this by modifying the shortcut (icon) to your game.
Example: "C:Program FilesNeed For Speed Hot Pursuit 2NfsHS.exe" (parameter)

Code - Result:

+ghost - Car is Transparent to Others
+opentree - Enter Locked Events
+nofrustration - Disables Confirmations
+nomovie - Disables Movie Demos
+nomusic - Disables Music
+nosnd - Disable Sound FX
+noreverb - Disable Reverb
+nofrontend - No Menu
+helicoptersOnly - Cops Only Use Helicopters