Peakbagger

I'm trying to upgrade several PC's from XP Home to XP Pro while retaining most current settings but changing others that I specify. Most importantly, I want to bypass the product key and automatically join a domain. I created an installation point via nLite, and it seems to work fine but rather than perform an upgrade, it wants to either delete the existing installation or install into a new folder. When I add in the unattend parm 'NTUpgrade=Yes", it enters the product key, but will not join the domain. I can choose the "Upgrade" path when I run the GUI, but it prompts me for a product key. How then, can i perform an unattended upgrade from XP Home to XP pro and joina domain? thanks! trin