You'll need the "retail upgrade version" of XP Pro.
Startup XP Home, insert the XP Pro upgrade CD
and select the default "upgrade" option during setup.
Yes, you can upgrade XP Home to Professional. There is no special
upgrade version just for this, but the regular XP Professional
Upgrade works fine (although it doesn't say so on the box).
But are you sure you want to do this? Are you aware that XP Home
and Professional are identical except that Professional includes
a few features (mostly related to security and networking)
missing from Home? Most home users don't need and would never use
these extra features and will see no benefits by upgrading.
