just had a quick read of this

http://www.gigabyte.com/MicroSite/185/on-off-charge.htm

Is that what your talking about? Do you want to stop it charging when system is off or just stop it changing to quick charge when system is on?

can you uninstall the driver, it says at the bottom of that link that you need a driver to use it so i say uninstall it if you don't need it?