programmatically change ListPreference options and keep the change permanent

I saw a couple of posts about changing the options programmatically but none of them say if that change is permanent.

What I want is basically to change the xml file that contains these options, the only problem is I dont know where it is or if it kept and read from everytime the app comes up.

Clarification: I have a ListPreference which is created from xml file, its arrays of entries and values are also defined in an xml with certain options. I would like to programmatically change these options (delete/add)

Thanks!