Parameter return to default state at every update

[fits79]

Why every time i update the firefox one parameter is return to each default state(true)?

I try use the user.js file at profile folder with these settings:

//Drag & drop links to folders
user_pref("browser.launcherProcess.enabled", false);

but doesn't work when i try to change the parameter through "about:config" at true and restart the firefox.
So it doesn't work at firefox update to.
I try to save the "user.js" file with notepad, wordpad, word(Office 2003) but neither work.

Why is that happening and how i can solve it?