[Windsun]

You can just add them into the "font family" box.

The default comes with something like this:

verdana, geneva, lucida, 'lucida grande', arial, helvetica, sans-serif

As an example to make the newer Vista font the first choice default, you would just add as the first selector, like this:

segoe ui,verdana, geneva, lucida, 'lucida grande', arial, helvetica, sans-serif

(segoe ui is the cleartype sans serif font nearest to verdana).