Get the versions and SPs on the current machine (default), or an array of machines piped in.

Get-DotNetVersion.ps1

function Get-DotNetVersion {
    [cmdletbinding()]
    Param(
        [Parameter(ValueFromPipeline=$True)] [object] $ComputerName
    )
    BEGIN {
    }
    PROCESS {
        if (-not $ComputerName) {
            $ComputerName = $env:COMPUTERNAME
        }

        $command = {
            function Get-NetCommonName([string]$version, $release) {
                if (-not $version) {
                  ""
                }
                elseif ($version.StartsWith("2.0")) {
                    "2.0"
                }
                elseif ($version.StartsWith("3.0")) {
                    "3.0"
                }
                elseif ($version.StartsWith("3.5")) {
                    "3.5"
                }
                elseif ($version.StartsWith("4.0")) {
                    "4.0"
                }
                elseif ($release -eq 378389) {
                    "4.5.0"
                }
                elseif ($release -eq 378675 -or $release -eq 378758) {
                    "4.5.1"
                }
                elseif ($release -eq 379893) {
                    "4.5.2"
                }
                elseif ($release -eq 393295 -or $release -eq 393297) {
                    "4.6.0"
                }
                elseif ($release -eq 394254 -or $release -eq 394271) {
                    "4.6.1"
                }
                elseif ($release -gt 394271) {
                    "> 4.6.1"
                }
                else {
                    ""
                }
            }
            $properties = (Get-ChildItem 'HKLM:\SOFTWARE\Microsoft\NET Framework Setup\NDP' -recurse |
            Get-ItemProperty -name Version,Release,SP -EA 0 |
            Where { $_.PSChildName -match '^(?!S)\p{L}' -and -not $_.PSChildName.StartsWith("Windows")})
            $properties | ?{ $_.Version -ne $null } | %{  $_ | Add-Member -NotePropertyName CommonName -NotePropertyValue $(Get-NetCommonName $_.Version $_.Release) }
            $properties | ft PSChildName, Version, SP, Release, CommonName
        }
        Invoke-Command -ComputerName $computerName -ScriptBlock $command
    }
}