Thanks smorizio!
I have a little more info:
Since I wanted to have UEFI like before, I'd left the setting (Legacy Support: "Disabled") but apparently this was preventing the SSD from being recognized (happens also with USB bootable disks). So I went back to BIOS settings and changed "Legacy Support" to "Enabled" and this time Windows installation found the SSD (as a single volume). I did not click "New" or "Format" options since I saw that the "Next" button is enabled. So I pressed that and the installation commenced. Soon installation restarted, this time showing a partitioned SSD. I chose the primary partition to install Windows. Installation completed successfully. Windows starts and all but I also get the warning that the onboard RAID cache SSD for rapid boot (which came installed with the pc) is now disabled. When I change Legacy Support back to "Disabled" Windows does not start.. And finally, the SSD still does not show up in BIOS. But I don't know if it's supposed to...
I tried to reinstall Windows (now that the SSD is formatted and partioned) but Windows installation still can't find it if "Legacy Support" is disabled.
So now the question is, how can I have "Legacy Support" Disabled and more importantly, Intel Rapid Storage Technology enabled once more (the 30 GB SSD to be enabled).
Thanks!