[Users] Run Once won't change boot sequence

Hello again, to install my VMs, I create them without CDROM and booting firstly from the HD. Then I go and choose "Run Once" and choose the ISO I want to use and boot from CDROM, on boot options. After installing the OS, I reboot and the first boot is again the CDROM. I have to shutdown the VM so the configuration chosen with HD being the first boot option is again the default. Alex