Here is a simple code if u want all the cars and tracks. First go to my
computer and click on drive D or C (were ever u installed your game.)
Then scroll down till u see a folder called TRACKS. Click on it and then
click on another file that say tracks and u will see that every track is
copied in a neat order. And u will see the word (example:)
m_prices(2)=30,000 just change that 30,000 into zero and when u are done
exit out and it will say do u want to save click yes. then exit out of
the file and the folder and look for a file called Cars and do the same
thing click on it and click on another file called cars. And it will
neatly show each car in order. For example scroll down to your favorite
car (Mercedes Benz clk_gtr) and change your favorites car price and nfs
price to zero.
Note: when u change nfs price to zero  the nfs edition car will cost
only 2,000. Then u can change all of them. Get out of the folder and
save when it asks u and exit everything out. Click on your game and
single race and if u want to change track it will be on 0 just unlock it
without paying and something with the cars except nfs edition