Well, I don't know what went wrong there.  Does anyone else?  If so, lend a hand here.

     See if there is a folder icon with a subtraction sign ("-") at the bottom of the library when you select that problem library folder.  If so, use that to remove that library from the P10 collection.  Then re-add it.

     I don't know the particulars of your "slave drive", but in general terms, yes, you can reference a remote library, such as one on a network aethernet drive or on a USB external hard drive, a (big honkin') flash drive, or an express card (great option for laptops).

express card (flash memory with SATA connection),  look for a slot on the right side of your laptop, near the front edge: .

Poser 12, in feet.  

OSes:  Win7Prox64, Win7Ultx64

Silo Pro 2.5.6 64bit, Vue Infinite 2014.7, Genetica 4.0 Studio, UV Mapper Pro, UV Layout Pro, PhotoImpact X3, GIF Animator 5