Windows XP Home Edition
Contains basic support for security among multiple users.
Built-in support for peer-to-peer networking, but only for up to five computers.
The backup utlity is not installed by default, but is included on the CD.
Windows XP Professional Edition
Includes extended support for security between multiple users on the same machine.
Better support for peer-to-peer networking, plus support for joining a "Windows NT domain."
The backup utlity is installed by default.
The Professional edition includes the following components not found in the Home edition:
Administrative Tools (in the Start Menu and Control Panel)
Automated System Recovery (ASR)
Boot Configuration Manager
Group Policy Refresh Utility
Multi-lingual User Interface (MUI) add-on
NTFS Encryption Utilitiy
Offline Files and Folders
Performance Log Manager
Scheduled Tasks Console
Security Template Utility
Provides support for multi-processor systems (2 or 4 CPUs), Dynamic Disks, Fax.