Isn't there a way to set it in the registry too ?
BTW, there's a project I read about on Slashdot a week or so back and I'll be damned if I can remember the guys doing it, but there's an effort to create apps that will run on a memory stick and remember thier settings on the stick and not your puter - I'm sure they mentioned firefox / thunderbird.
That would be damn awesome - the ability to just plug in your stick and have access to your email directly on any PC.