Check sound mixer(Primary SD). Sometimes it has effects. I have to ask, why don't you just use your ASIO as primary sd? Or do you mean windows sd as a "primary"? Anyway switch drivers is all you need i think.
edit: Also check daw audio functions. I have no idea how fl works, so can't say anything. But in my daw I can choose between Windows Wave, 5.1, asio, usb digital, usb interface, D sound(or something).. I don't remember them all.