Convert Mac Pro internal boot drive into an external harddrive without wiping I have a 2008 Mac Pro running Yosemite. I just purchased a solid state hard drive which I want to become my boot drive. I do not want to transfer the data from the original boot drive to the solid state drive; I just want to be able to access the data on it.

Is there a way to move it to another slot and not have it run as a boot drive, so I may access the contents?

and/or

Is there a way to essentially turn it into an external hard drive, so I can easily access the contents?

Thank you
You don't even need to move it to another slot. Install your SSD, set it up the way you want, then go to System Preferences -> Startup Disk and choose the SSD.

This isn't Windows, and it isn't 1993. You can have as many bootable volumes online as you have disk space for, Macs boot the one you want booted.