Could not use Powershell scripts even after reading a lot about loading snap-ins/modules but I probably missed something. :-/
So I installed VMware-vSphere-CLI (version 5.5.0 for me) so I had the vmware-cmd.pl script and commands so that I could run the following DOS script by a scheduled task :
cd /D "C:\Program Files (x86)\VMware\VMware vSphere CLI\bin"
set login=-H myserver -U root -P mypassword
rem vmware-cmd.pl %login% -l to get the VM raw name
set vm=/vmfs/volumes/53b17247-36fb17f7-93f8-002590534d58/VM/VM.vmx
rem If I can get the VMtools status, the OS runs in the VM, so I shutdown the guest. Otherwise, I only have to hard shutdown the VM.
vmware-cmd.pl %login% %vm% gettoolslastactive | findstr /C:"= 0"
if %ERRORLEVEL% == 0 (
vmware-cmd.pl %login% %vm% stop hard
) else (
vmware-cmd.pl %login% %vm% stop
)