#Get-UnusedComputers.ps1
#
#Alan dot Kaplan at va dot gov
#alan at akaplan dot com
#2/13/16

WorkFlow Check-Unused {
param([string[]]$computers)
    ForEach -parallel ($Computer in $computers){
    InLineScript{
    $Error.Clear()
    $BOnline = $false
    $lastLogon = ""
    $bOnline = "unknown"
    $UserPath =""
    
    $bOnline = Test-Connection -quiet -Count 1 -ComputerName $using:Computer
        if ($bOnline -eq $true){
          Try{
            $localPathList = get-wmiobject -ComputerName $using:Computer -query "Select localpath from Win32_UserProfile Where Special = 'False'"  -ErrorAction Stop |
            select  -ExpandProperty localpath
            $logons = $localPathList | % {
            $UNC ="\\$using:Computer\"+$_.ToString().Replace(":","$")
           if (test-path $UNC) {gi $UNC}
            } 
            $lastLogonNfo = $logons | sort lastwritetime -Descending | select name, LastWriteTime -First 1
            $lastLogon = ($lastLogonNfo).LastWriteTime.tostring().trim()
            $UserPath = ($lastLogonNFO).name.tostring().trim()
          }Catch{}
     }
     $output = [PSCustomObject]@{
     HostName = $using:Computer
     LastLogon=$lastLogon
     LastUser = $UserPath
     Online = $bOnline
     Error = $Error[0].Exception.Message
     }
    return $output
  }#End Inline
 } #End Foreach
}#End WorkFlow 

#Examples for input
$OU = 'OU=Workstations,DC=MyCo,DC=com'
$computers = (Get-adComputer -searchbase $OU -filter * -searchscope subtree).name


$LastLogonInfo = Check-Unused $computers
$LastLogonInfo | select * -ExcludeProperty ps* |
Export-Csv -Path $env:userprofile\Desktop\InactiveComputers.csv -NoTypeInformation