I made the change to the preferences.txt file located in the programfiles/arduino/lib folder.
In my copy of 1.0.6, the preferences.txt is under my user account:
C:\Users\Ray\AppData\Roaming\Arduino\preferences.txt
I got the path by doing File - Preferences, then it shows up at the bottom of that screen. Might be worth checking on your system, in case there are two copies of the preference file.