Yeah, it's a little odd. It does look legitimate, but I can't imagine HP sent a non-OEM upgrade. It could be part of the problem, though, and Microsoft finally got around to deciding something was up (it can take up to 180 days from the last licensing check-in for something like that to occur, although it's usually quicker). It's probably worth making the phone call and taking the 5 minutes to get them to update things for you and fix the activation. I don't think mixing a retail upgrade over an OEM install is a good idea, but it should have continued working.