Connect-VIServer -Server <IP of DNS name of Vcenter> -user <NETBIOSDomain\username> -password <password>
$VMs = Get-VM
foreach ($vm in $VMs)
{
$ToolsStatus = $vm.ExtensionData.Guest.ToolsStatus
if ($ToolsStatus -ne "toolsOK")
{
Write-Host "Updating the tools of" $VM.Name
$vm | Update-Tools -NoReboot
}
}