Com base no seu PS existente, você quer algo para ajudar a determinar computadores antigos no AD.
Você pode executar o PS aqui :
# Gets time stamps for all computers in the domain that have NOT logged in since after specified date
# Mod by Tilo 2013-08-27
import-module activedirectory
$domain = "domain.mydom.com"
$DaysInactive = 90
$time = (Get-Date).Adddays(-($DaysInactive))
# Get all AD computers with lastLogonTimestamp less than our time
Get-ADComputer -Filter {LastLogonTimeStamp -lt $time} -Properties LastLogonTimeStamp |
# Output hostname and lastLogonTimestamp into CSV
select-object Name,@{Name="Stamp"; Expression={[DateTime]::FromFileTime($_.lastLogonTimestamp)}} | export-csv OLD_Computer.csv -notypeinformation
Ou meu favorito pessoal de longa data da JoeWare: