Personally, Windows XP Home version has all the features you'd need, except for the below functions which are mostly used in a corporate environment.
BarryZ, 1USA
Remote Desktop - displaying the desktop on another computer for tech support.
There's a 3rd party program that 1USA uses to do the same thing.
IIS - Internet Information Services - hosting a website.
Neither version of XP has sufficient security to bare the computer for anonymous visits to websites, and frequently results in a hacked computer. Use Windows 2003 Server for websites instead. Duhhh.
In addition, XP Pro installs SQL Server software into the Services. SQL Server runs by default. You need to know enough to turn it off -- so that your computer isn't hackable ... because it doesn't retrieve all the Security Updates. This becomes a very big security hole.
Offline File Folders: If you want to access your computer from elsewhere, use the 3rd party program that 1USA uses, and it's NOT that Go2MyPC junk.
Access Control: Pro has more details to control access to your computer, specifically when setting up XP as a server using IIS... which shouldn't be done as mentioned above.
Sharing a folder shouldn't be done either... because anyone can place an .exe file into a shared folder... which could turn off the Firewall and anti-virus software... and lead to a full-scale hack attack. Again, if you want to securely share items, use a 1USA server.
Membership in a Corporate Domain: Pro has lots of features in it to identify Domains and allow certain other computers access to its files - specifically for on a corporate network.
This includes the valuable Remote Installation Service (RIS) ? which is support for remote operating system installations where desktops can be added to a corporate network from across the network.
Other than that? Save your money and buy XP Home edition. XP Home can be part of a network, XP Home can do all of the graphical things that Pro can do. Simply add any 3rd party software to have it do what you need it to do.
1USA Members can click on the below Link to see the Checklist comparison of features.