I have done a clean install of ubuntu 16.04 LTS onto a acer aspire VN7-792G. This has a 128Gb SDD and a 1Tb HDD. The laptop was supplied with windows 10, which I removed using the diskpart utility and clean (for the SDD) or clean all (for the HDD) commands.
The HDD can be found from the terminal with the fdisk -l command, but is not shown on the launcher or in the "computer" window.
I'm guessing that the first stage to correcting this is to assign the HDD (disk /dev/sdb) a UUID, as it does not currently appear to have one (screenshot of fdisk -l and blkid output attached)?