Here is some info dealing with XP Home and Pro editions and networking:
Specific differences in networking functions between Windows XP Home Edition and Professional Edition include:
Simultaneous file sharing connections supported--five with Home Edition, ten with Professional Edition
Professional Edition supports domains for added security and management. Domain level network management software can't be used with Home Edition.
Professional Edition adds levels of access to shared files and folders beyond the basic access supported by the Home Edition. For example, you can control which users have access to files and how many users can have simultaneous access.
With Professional Edition, you can manually set up and manage IP security, with protection for protocols, including L2TP (Layer 2 Tunneling Protocol). You'll need to use Professional for example, if you want use a VPN (Virtual Private Network) with IPSec (IP security - a standard TCP/IP protection protocol).
If you connect to Novell Netware-based networks, Professional Edition is required to access Netware file and print resources via Netware Client Services.