You don't need it. If you're using SATA drives you don't need a jumper. I thought you would need one to make a SATA 300 drive work with a SATA 150 computer, but it worked fine without, even switching to the slower speed. If it's IDE, pull one off of your motherboard (if there are spares) or other hard drives. You may be able to configure it without a jumper inserted using cable select or making your other drive either master or slave (depending what your new drive sets itself to without a jumper).