OK, that's more clear. Are both of the drives SATA?
The "second power supply cable" is square - four holes - and it comes out of the power supply and mounts in a different place on some motherboards from the long connector. Depends on the brand...
Yes...
That power cord from the power suppler even says 'CPU' on the connector and IS plugged into the m/b properly.
Both drives are SATA.
As with yourself and many here, I've built many of my own computers for years but the last one WAS my DAW and it was 10 years ago....obviously I'm out of the current knowledge loop with these painful h/w upgrading protocols.
I really am leaning to the issue of re-authorization being necessary for this m/b change.
Many thanks for even reading my plea...