How to create power config schemes on clients at machine start?

Question

I set up a machine startup batch script & confirmed it's fired. However it couldn't create any power scheme on XP client which one a domain member.

This is the batch file:

   dir > c:\_RUN-OK.txt

   powercfg /create "custom"
   powercfg /change "custom" /monitor-timeout-ac 10
   powercfg /setactive "custom"

Why I couldn't create & set a custom scheme? Is it a privilege problem? Because of startup scripts run in Systems (machine) context?