I just put an old PC laptop hard drive into a USB enclosure and tried plugging it into the mac but it doesn't show up on the OS. I've got nothing on it of importance on the drive, I just want to be able to use it for storage in the future. Preferably it be PC formatted, but mac formatted is fine. Any thoughts on how I can get it to work? I'm new to all of this, but enjoying my new machine so far!