GMAN wrote:
Make sure that the SATA ports you are trying to put those adapters on in the
BIOS are set for Compatilbe and NOT AHCI or enhanced

Sorry for the delay in reporting back.
At your advice, I toggled the Bios settings as follows:
SATA Mode: 'ACHI Mode' (default) = 'IDE Mode'
Serial-ATA Controller 0: 'Enhanced' (default) = 'Compatible'
Serial-ATA Controller 1: 'Enhanced' (default) unchanged

Still no joy, though. My new SATA Plextor shows up but the older IDE Plextor is
still unrecognized. Looks like a classic case of "Lost in Translation" :-)
--
Tom McCreadie