List of differences between XP and Home

• The ability to become part of a Windows Server domain, a group of computers that are remotely managed by one or more central servers.
• A sophisticated access control scheme that allows specific permissions on files to be granted to specific users under normal circumstances. However, users can use tools other than Windows Explorer (like cacls or File Manager), or restart to Safe Mode to modify access control lists.
• Remote Desktop server, which allows a PC to be operated by another Windows XP user over a local area network or the Internet.
• Offline Files and Folders, which allow the PC to automatically store a copy of files from another networked computer and work with them while disconnected from the network.
• Encrypting File System, which encrypts files stored on the computer's hard drive so they cannot be read by another user, even with physical access to the storage medium.
• Centralized administration features, including Group Policies, Automatic Software Installation and Maintenance, Roaming User Profiles, and Remote Installation Service (RIS).
• Internet Information Services (IIS), Microsoft's HTTP and FTP Server.
• Support for two physical central processing units (CPU). (Because the number of CPU cores and Hyper-threading capabilities on modern CPUs are considered to be part of a single physical processor, multicore CPUs are supported using XP Home Edition.)
• Windows Management Instrumentation Console (WMIC): WMIC is a command-line tool designed to ease WMI information retrieval about a system by using simple keywords (aliases).

(source: wikipedia)