does anyone know of a way to replace austerity with another theme as the default. i've been looking through all the code, but can't find where it loads the default theme. thanks.

What do you mean, the "switch to default theme" shortcut?
In your litestep main directory there is a shortcut labeled "switch to default theme" open its properties and change it to this:
c:\litestep\utilities\LSThemeInstaller "/switch" "[b]whatever theme name you want[\b]"

Everything except the bold should be the same.

does the bold tag work?