Specifying where to safe prefs?

Hi!

I'm currently creating an app that will be run with autostart on a CD.
Althow, when I try to save a preference, it won't save. And I think it
has to do with that it's trying to write to the CD. Is there a way to
specify where the preferences should be saved, like the profile-folder?

And also, if there isn't any Firefox previosly installed on the machine
running the CD, will the app (which builds on Firefox, duh) automaticly
create such?

Thanks in advance!
Yours,
Sven Andersson, Sweden