29th February only comes once in four years and this 29th February 2012 has been the day of Microsoft beta. First Windows 8 Consumer Preview was released followed by Windows Server 8 beta and then .NET Framework 4.5 beta and Visual Studio 11 for Windows 8. dotNET framework 4.5 has been specifically designed for developers who want to build Metro style apps for Windows 8 using C# and Visual Basic .NET. It can be used along with Visual Studio 11 for development of the new apps. I have written about .NET Framework 4.5 Developer Preview before.
.NET Framework 4.5 is only designed to be used on Windows 7 or Windows 8. You will not be able to install it on Windows XP or even Windows Vista. You will have to be content with .NET Framework 4 for those Operating Systems.
According to Microsoft:
The Microsoft .NET Framework 4.5 Beta is a highly compatible, in-place update to the .NET Framework 4. By using the .NET Framework 4.5 Beta together with the C# or Visual Basic programming languages, you can write Windows Metro style apps. The .NET Framework 4.5 Beta includes significant language and framework enhancements for C# and Visual Basic so that you can harness asynchrony, the blending of control flow in synchronous code, a responsive UI, and web app scalability. The .NET Framework 4.5 Beta adds substantial improvements to other functional areas such as ASP.NET, Managed Extensibility Framework (MEF), Windows Communication Foundation (WCF), Windows Workflow Foundation (WF), and Windows Identity Foundation (WIF). The .NET Framework 4.5 Beta delivers better performance, reliability, and security.
Download .NET Framework 4.5 for 32-bit and 64-bit Operating Systems:
Download .NET Framework 4.5 Offline Installer 32-bit and 64-bit (49.7 MB) [Direct Download]
The same installer can be used for both 32-bit and 64-bit Operating System. The compatible Operating Systems include Windows 7, Windows 8, Windows Server 2008 and Windows Server 8 beta. This is a multi-language installer. If you want .NET Framework 4.5 in your own language, you can download it from below links:
All these downloads are language packs only. You will need to have the original .NET Framework 4.5 to be installed in order to convert it to any other language.