Hi John (et al) I am going to assume these are drives formatted NTFS. Of late I have encountered drives from Windows machines which Linux won't mount, I think ntfs-3g is a bit finicky about this in recent versions. Get in touch with me directly if you wish, I have a gadget which will connect drives via USB to avoid having to put them into a machine. Some distributions may be able to see the drives even if Mint doesn't wish to, we could try various versions.