|You need to explain a bit more as to what you are trying to do.|
You can have a Primary Slave and a Primary Master
You can have a Secondary Slave and a Secondary Master.
Primary and secondary is determined by which interface on the motherboard the cable is plugged into.
Master and Slave is determined by jumpers on the hard disk.
If you want to change which disk the computer boots from that can be done in the BIOS as most BIOS these days can boot from a slave drive or any bootable drive in the system. Gone are the days when you could only boot from the Primary Master.
This assumes you are using P/ATA drives.
If they are SATA non of the above applies.