Windows won't boot with Sansa Fuze plugged in

it sounds like even though there is no legacy usb option in your bios something there is still causing the issue. you could check to see if there is a bios update available for your motherboard that may resolve the issue but that is kind of a long shot. do you see the issue with any other USB mass storage device? also are you using MTP or MSC mode on the fuze? if you have not tried both I would and see if you get the same result.