osversion.ps1

function Get-OSVersion {
	$basic_version = [System.Environment]::OSVersion.Version
	$basic_version_string = '{0}.{1}.{2}' -f $basic_version.Major, $basic_version.Minor, $basic_version.Build

	# only take the 10 most recently modified .dll/.exe files to speed this up
	$system32 = (ls "$env:SystemRoot\System32" | ? { $_.Name -match ".*win.*(\.dll|\.exe)$" } | sort LastWriteTime -Descending)[0..9] 
	
	$versions = $system32 | % { 
		$obj = New-Object PSObject
		$obj | Add-Member NoteProperty Version((Get-ItemProperty -Path $_.Fullname).VersionInfo.FileVersion)
		return $obj 
	}
	
	$versions = $versions | ? { $_.Version -match $basic_version_string }                                          
	
	$regex = '\((\w+)\.(\d+-\d+)\)'
	$versions = $versions | % { 
		$spl = $_.Version -split " "
		if ($spl[1] -match $regex) {
			$_.Version = $spl[0]
			$_ | Add-Member NoteProperty BuildDate($matches[2])
			return $_ 
		}
	} | sort -Property BuildDate -Descending
	
	if ($versions.Length) {
		return $versions[0].Version
	} else {
		return $basic_version_string
	}
}