You can use WMI like this if you want to change a service start mode:
([wmi]'Win32_Service.Name="Spooler"').ChangeStartMode('Automatic').ReturnValue ([wmi]'Win32_Service.Name="Spooler"').ChangeStartMode('Manual').ReturnValue
Note that a return value of 0 indicates success. You will need Administrator privileges to change the start mode.
