The .Net Framework is the most significant product in Microsoft's recent history and version 2.0 is available for download right now (from the links below). It isn't yet available from Windows Update, but that should only be a matter of time.
Microsoft .NET Framework Version 2.0 Redistributable Package for (x86)
Windows 2000; Windows 98; Windows 98 Second Edition; Windows ME; Windows Server 2003; Windows XP
Microsoft .NET Framework Version 2.0 Redistributable Package for (IA64)
Windows Server 2003, Datacenter Edition for 64-Bit Itanium-Based Systems; Windows Server 2003, Enterprise Edition for Itanium-based Systems; Windows XP for Itanium-based Systems Version 2003
Microsoft .NET Framework Version 2.0 Redistributable Package for (x64)
Windows Server 2003, Datacenter x64 Edition; Windows Server 2003, Enterprise x64 Edition; Windows Server 2003, Standard x64 Edition; Windows XP 64-bit