a burner has to officially support any given speed in order for it to even be an option. for example, most modern cd burners no longer support writing at speeds lower than 4x. another example would be my 1300A, which can't write dvds at 1x, only 2x or above. this kind of thing isn't only specific to the lowest burn speeds either; a cd burner might offer 16x and 24x recording, but not 20x. if the drive itself doesn't offer the specific speed, then u can't write at that speed.