I've had intermittent SATA issues with my current motherboard since almost forever. Sometimes it just won't boot, or (sometimes) even post if a hdd is connected. If I disconnect the drive, boot up with a cd (my go-to is systemrescuecd, haven't really tried it with anything else), power down and reconnect the drive, it seems to reset the bios (or something) and then the pc can be booted with the drive connected, even if the hdd itself won't boot.

OK, that's good to know. Thanks!

heard about this windows 10 failed update in other platform also and I also heard that Windows makers are working on it. Its a software issue nothing to do with hardware. 

Trying it now on a seriously underspecced virtualbox clone of Windows 7. The container is only 30G, so I had to dump a whole lotta stuff (which is ok because I should have done it anyway). Also since it's a clone, I had to do the GWA check and start over (including the initial download  >-| ). It's unsurprisingly super slow with only 2G of assigned memory, but is at least proceeding

And it took.  :-O~~~