Upgrading W2K AD on AS to W2K3 on Std

I just purchases the MS Midsized Business Promo which includes Exchange 2003 and 3 copies of W2K3 Standard Server. I want to upgrade my Active Directory but both of my current DC’s are on Windows 2000 Advanced server. What is the best/safest way to get my 2000 AS DC’s converted to 2003 standard server since you cannot upgrade from 2000 AS to 2003 Standard.