WMF 5.1 Release Notes: https://msdn.microsoft.com/en-us/powershell/wmf/5.1/release-notes

  2017.01.26  (5.1.14409.1005)
    -  New: Installs WMF 5.1
    -  Tested On: Win7 + PSH 2, Win7 + WMF 3, Win 8.1 + WMF 4, 2012 R2 + WMF 5.0, Windows 10
    -  EXPERIMENTAL: Attempts to Preserve the PSModulePath when WMF 5.1 is 
                     installed over WMF 3 on Windows 7 or Server 2008.

         How it the experimental support works:
           *) It only takes effect on Windows 7 and Server 2008 R2 and only if WMF 3 is installed
           *) You must pre-install at least .NET 4.5.1 (required by WMF 4 and later)
           *) You must use the -force switch on the package

           What steps are taken to preserve PSModulePath:
              1) The custom parts of the PSModulePath backed up to BackupPSModulePath
              2) A fix up script that appends those values to the PSModulePath is written to:
                       %WINDIR%\Temp\psmodulepathfixup.ps1
              3) A scheduled task is setup for the next reboot that runs the fix up script

           If you find that #3 does not work correctly, then you can use #1 or #2 with some of your 
           own automation to recover from the PsModulePath overwrite.

  2016.12.01  (5.0.10586.20170115)
    -  Fixed: Package generates error that you must upgrade to Windows 8.1 on Server 2012 (not-R2) domain controllers.

  2016.12.01  (5.0.10586.20161201)
    -  IMPORTANT: This package no longer updates a machine to an older version of PowerShell when 5 cannot be applied, the package must
         be explicitly called with the -version parameter if the system being configured cannot take PowerShell 5.
    -  Updated to use checksums
    -  Updated to use re-released MSUs discussed here (old ones getting 404s):
         https://blogs.msdn.microsoft.com/powershell/2016/02/24/windows-management-framework-wmf-5-0-rtm-packages-has-been-republished/
    -  Checks and errors if Windows Update service is disabled, the error message suggests enabling it just for the time this package runs
         (it is a common good practice to disable Windows Update when doing long running orchestration,
         however, it must be enabled for this package to run)

    2016.3.28:
			Fixed bug with Windows Server 2012 installation

		2015.12.19:
    Updated for PowerShell 5.0.10586.20151218 RTM - Released 2015-12-18.

  2015.09.02:
    Updated for PowerShell 5.0.10514.6 (Production Preview) Released 8/31/15 (Darwin).
			Checks if you already have 5.0 installed and requires previous versions of 5 to be uninstalled first.

		2015.04.29:
    Updated for PowerShell 5.0.10105 (April 2015 Preview) (Darwin).
			Windows 7 SP1 and Server 2008 R2 SP1 NOW SUPPORTED FOR PSH 5!

  2015.03.18:
    Updated for PowerShell 5 (Darwin).

		2014.10.01:
    Changed to report success when PowerShell 4.0 is already installed.

  2014.09.15:
    Support added for PowerShell 4.0