In my Ingest Sources dialog I have two disks appearing that I will NEVER Ingest from.  I only ingest from a card reader (F:).  The two disks are:
E:\  [Scratch] (16.3 GB used)
Z:\  [Server] (1422.1 GB used)
I want to get rid of them, but when I try the UNMOUNT, I get "Unable to Unmount the selected volumes".
I certainly don't want PM to ever search the Z: Server drive as it's pretty damn large and has lots of images on it.
What can I do?