PowerShell - Get a list of "old" computers in Active Directory

# Requires ActiveRoles CmdLets from Quest Software (They're free and awesome) - http://www.quest.com/powershell/activeroles-server
$old = (Get-Date).AddDays(-60) # Modify the -60 to match your threshold 
Get-QADComputer -IncludedProperties pwdLastSet -SizeLimit 0 | where { $_.pwdLastSet -le $old }