What does WindowsXP Professional Edition bring along for the ride, over and above Home Edition??

    * Multiprocessor support. XP Professional supports up to 2 processors in an SMP system.
    * Greater Security. Not only does Pro support NTFS, but it also supports encrytion within the filesystem.
    * Remote Desktop Administration. Based on Windows Terminal Services, XP Pro, allows you secure remote access to your systems desktop, over a LAN or WAN (such as the internet).
    * Greater Access Control. Administrators can more effectively limit users acess to files, programs, and system devices and resources.
    * Support for Offline files/folders. You can acess files and folders on a network share, when disconnected from the server.
    * Domain Support. WindowsXP Pro can login to Windows network domains.
    * Roaming User Profiles, allowing access to your profile from anywhere on the network.
    * Group Policies. Allows the administrations of users and machines as "Groups" or "classes", simplifying network administration.
    * Microsoft Internet Information Services. WindowsXP Professional includes the IIS Web Server 5.1.

Again, as with Home edition, there are even more features than the ones I indicate above, but these are the primary additions/distictions between XP Home Edition, and XP Professional.

What about the upgrade path though? Which operating systems are supported as "upgrades"??