I bought both successfully last year also. This is a recent change. I've already returned the WD's (my book); & the Seagate (Expansion) is boxed up waiting for a label.
Did you read the article I linked to above? That appears to correctly explain the problem.It also explains clearly what I see. I need to find "legacy" drives (6 months ago?)
I've spent 2 hours on the phone. WD gave me incorrect info, & several say they are XP compatible & are not. No one locally has any older stock that I can find.
I have an email into Buffalo, who SUPPOSEDLY hasn't made the change; to be honest after getting invalid info from a WD rep on the phone, I'm a bit frightened to waste $ on mail order, where returns can be expensive.
I tried calling Seagate; waited 20 minutes for what I was told would be a 1 minute hold & gave up. I'm at the point where I would buy refurbed drives if they were the right size & worked with XP.
What really bites is this was basically done in secret; I would have stocked up if I had known.