It doesn't work that way on any system I've seen, not if it has an OS that does USB and optical drives. Maybe if you say what OS you are running and the exact hardware (USB 1.1, USB 2.0, bus-powered or external powered optical drive, etc.) someone will have suggestions to make. If I remember correctly, for instance, Windows XP got USB 2.0 support in one of its service packs. If you stuck a USB 2.0 card in a system running that OS running at a service pack level that didn't support it I'm not sure how it would behave. I would hope that it would still detect at boot time and just run as USB 1.1, but who knows?