How do I turn my optibay hard drive into a slave storage? I have a new SSD and my old hard drive installed in my optibay. My old hard drive currently has a Mac OS system on it, and I want to just wipe it so I can use it for storing my videos, and pictures. How can I do this?
Can you boot into the laptop from the SSD OS while both drives are in your laptop?

If so, just open disk utility, select your old HDD drive, and select the erase tab.

From there you can reformat your hard drive.