This is more of an observation I thought I would share.
I started a major SBS 2003 install for a real estate company last weekend involving two location, 40 workstations and a VPN tunnel.
Many of the client computers had XP home installed so the owners purchased many OEM XP Professional upgrades.
In cases where the XP Home user had upgraded to Internet Explorer 7, the XP Pro upgrade fails at activation. A moobe.exe error (Microsoft Out of Box Expereince) error is generated and the activation never completes.
If the client had IE 6, the upgrade installs successfully.