Yes, one can upgrade Windows XP Home to Windows XP Pro:
1. Purchase the conventional "retail upgrade version" of Windows XP Pro.
2. Uninstall any third-party antivirus or firewall programs.
3. Disconnect all peripheral hardware devices, but not the monitor, keyboard or mouse.
4. While at your XP Home desktop screen, insert the XP Pro CD in the CD drive.
5. Select the default "Upgrade" option....do not select "New Installation".
6. Reinstall your antivirus program & turn-on the firewall.
7. Visit the Windows Update website and download the necessary updates.
8. Perform a Disk Cleanup and Defrag your hard drive afterward.
--
Carey Frisch
Microsoft MVP
Windows XP - Shell/User
Be Smart! Protect your PC!
http://www.microsoft.com/security/protect/