It requires modifying the installation CD (just two bytes), but for the brave: HOWTO Change Windows XP Home to Windows XP Pro – Gizmodo
Lessee, judging by Microsoft’s Windows XP Comparison Guide, that should get you:
Fast User Switching
- Offline Files
- Remote Desktop
- hardware support (Dynamic Disks, Multiple Processors)
- security (Access Control, EFS)
- IIS, and
- domain support (Group Policy, Assigned Software Installation, Roaming Profiles, RIS).
Of these features, everything but IIS and domain support can be useful to many home users.
In particular, there’s no way the first three — System Restore, NTBackup, and Fast User Switching — should have ever been left out of XP Home — ALL users could benefit from them. Whoops, had some bad info before I checked the XP Comparison Guide (and I was caught editing, so I can’t just erase it now! Good catch Ed!) — It looks like FUS and System Restore are in XP Home. My opinion stands for NTBackup and Remote Desktop, tho.