In the pictures one can see the SATA connector, with and without the hard disk.
Everything works fine. I was a little worried about the added load that the hard disk would give to the power supply but I didn’t really expect any ptoblem.
Now I have to find room for the hard drive inside an already cramped space. I think that probably I will be forced to replace two big 1500u 6.3V capacitors to have enough space to fit the disk and close the thin client.
Anyway, the thin client operating system is now Debian, thanking the usb install procedure.
I already like the silence.