ASP.NET is available as free download and runs on the following platforms:
Microsoft Windows 2000 Professional and Server (SP 2 recommended)
Microsoft Windows XP Professional
Microsoft Windows .NET Server
.NET Framework Redistributable(21 MB)
This download includes ASP.NET and the .NET Framework, and provides everything necessary to build and deploy ASP.NET applications. This is the recommended installation package for production Web servers.
.NET Framework Software Development Kit(131 MB)
This download includes everything in the Redistributable, plus documentation, Quickstart samples, MSDE (a lightweight SQL database engine), and command-line tools and compilers.