Salutations!
My original HDD failed on my Aspire 5560G recently so I bought a SSD for it. Installed it with OS/Driver etc without a hitch. I then decided I wanted additional storage space so I bought an optic drive caddy for a 2nd HDD. I installed a 500G Seagate HDD in the caddy and replaced my optical drive with it.
When I booted it up for the first time, the laptop would not post or load anything. I then turned off the system, pulled the caddy out and the laptop booted up fine when I turned it back on. So I went in the BIOS and changed the boot order making the Primary HDD (SSD) boot first. Rebooted with the caddy back in and the same thing would happen. Didn't boot nor posted. I have to boot up without the caddy and then push it back in and the system would recognize the 2nd HDD.
I formatted the 2nd HDD and created a partition. Checked my BIOS version which is AcerSystem v2.2
It still won't boot with the HDD caddy installed. Any suggestions would be greatly appreciated 
PS. I have the same caddy on another laptop [not acer], no issues.
Optic Drive Caddy