The bios doesn't designate drives as master/slave, only SATA/IDE ports enabled/disabled. The master/slave listing is dependent on which sata port the drive is plugged into on the motherboard.
If this is a sata drive, then no need to worry as sata doesn't use master/slave, but will sometimes list it that way for legacy purposes.
If it's an IDE drive, master/slave is configured via jumpers on the hard drive. If there are no other IDE drives in the system then it should be configured as master or some drives have a setting for "single", though I haven't seen many drives with a "single" setting these days.