System will not boot properly when connecting older SATA HDDs

[star-gazer777]

I recently installed a brand new 1TB SSD, which for now is both my boot drive and data drive. I have a 512 GB flash drive I am temporarily using for backups.

I am now attempting to connect two older HDDs (WD 640GB SATA) so I can access previously stored docs, photos, graphics etc. When I connect them, the system will not even complete boot-up. I have tried connecting both at once, and also separately. I have connected them using different SATA ports, and I have used different SATA cables known to be good.

Also, all of the info I have found indicates that on newer systems, SATA HDDs do not require jumpers.

I have looked in BIOS, the SSD is selected as the boot drive (UEFI), and secondary boot is disabled.

What should I look at next? Thanks in advance ...

P.S. The two 640GB drives are identical. They were previously working fine, when I had a WD Raptor 250GB (10k rpm) as the boot drive.


SYSTEM:
P/S: Corsair CX750M
Mobo: Gigabyte 990FXA-UD5
CPU: AMD Phenom II X6 1090T
RAM: Patriot 16GB DDR-3 (PC3-14900)
Graphics: AMD Radeon R7-200 w/2GB vRAM
OS: Windows 10