With the release of Windows 8.1, Microsoft has also released .NET  Framework 4.5.1 and Visual Studio 2013. As Windows 8 comes with .NET Framework 4.5 installed, similarly Windows 8.1 also comes included with .NET Framework 4.5.1 by default. So you don’t need to install .NET 4.5.1 in Windows 8.1 and you can install this update in Windows 7 SP1 and Windows 8. "x64edit and continue" is significant addition in this release.

.NET 4.5.1 has been offered as in-place update to Microsoft .NET framework 4 and .NET framework 4.5 

Supported operating systems

Windows 7 Service Pack 1, Windows 8, Windows Server 2008 R2 SP1, Windows Server 2008 Service Pack 2, Windows Server 2012, Windows Vista Service Pack 2

You can download offline installer for .NET Framework 4.5.1 from here [66.8 MB] and here is the web installer link [997 KB].