[begin heated debate...] You don't need to buy the more expensive Windows XP Advanced Server or Windows 2000 Server to run IIS.
However, the XP Professional standard EULA (license) states that at most 10 computers may connect to your machine for IIS, File/Printing services, and remote access.
OK, first off I am NOT asking for help to hack my system or do anything shady.
I am installing the same copy of Windows XP that was originally on this computer when it was new (AKA, all legit, genuine product key, etc), and I'm trying to log on for the first time.
If you want a free solution and don't need ASP, you could also run Apache PHP on your XP Professional machine.
It loads a blue screen with the keys in the background, but nothing comes up after that--- no text, nothing at all, just a blank blue screen.
Of course, if I say "no" to activating windows now, then I get returned to the user logon screen.
With the introduction of Windows XP, the C based software-only GDI subsystem was introduced to replace certain GDI functions.
GDI adds anti-aliased 2D graphics, textures, floating point coordinates, gradient shading, more complex path management, bicubic filtering, intrinsic support for modern graphics-file formats like JPEG and PNG, and support for composition of affine transformations in the 2D view pipeline. Use of these features is apparent in Windows XP's user interface (transparent desktop icon labels, drop shadows for icon labels on the desktop, shadows under menus, translucent blue selection rectangle in Windows Explorer, sliding task panes and taskbar buttons), and several of its applications such as Microsoft Paint, Windows Picture and Fax Viewer, Photo Printing Wizard, My Pictures Slideshow screensaver, and their presence in the basic graphics layer greatly simplifies implementations of vector-graphics systems such as Flash or SVG.