The install directory for installing patches is as follows..
"C:\Program Files\Activision Value\Street Legal Racing\"..
There should be a text box in all patches where it asks you the patches are to be installed to if you like you can copy and paste that into the text box without the ".
Where you can get the patches from? Into another post in to the same area of this forum look for topic title "links to all street legal racing patches here"...install patches in order of which I have listed them in the topic.
This process should work fine for installing all game patches unless you have installed Street Legal into a diffrent directory or drive letter in which case click browse button on patch and browse to where you have the game installed to.
If you have diffculty in finding where game is installed right click on Street Legal icon and from menu that pops up select properties and you should see where it is installed from that.