Install OpalisRobot or follow this procedure to use the built in scheduler:
1. For each server, edit HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Lsa and add value SubmitControl as a REG_DWORD. Set it to 1.
2. For scheduling jobs on a Domain Controller, add the user to the Server Operators group. For an ordinary server, the user must be a member of the local Administrators group.
You must reboot the server(s) for the change to take effect.