[XeTeX] Is there an easy how-to use pgf with xelatex?

[Søren Christensen]

I use komascript letter-class and have both graphicx and pgf-commands,
what should I specify for driver?

I downloaded the MacTex-package (.dmg) from tug (I guess its TeXLive 2007,
so maybe I need to upgrade).

I got the error-message: "pgfsys-xetex.def" not found.

I would like to get a hint for a solution.

Thanks
Søren Christensen