Read it again. It works on Win2k, Windows XP Pro and XP Home. As quoted from the requirements page
ASP.NET Cassini Sample Web Server: System Requirements
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The ASP.NET Cassini Sample Web Server is available as free download, and runs on the following platforms:
Microsoft Windows 2000 Professional and Server (SP 2 recommended)
Microsoft Windows XP Professional or Home Edition
.NET Framework version 1.0