Previously (copy below) I wrote that the Windows 10 Memory Diagnostic Tool trick did not work for me, that all external SATA drives remained unrecognized by the OS despite trying every published software/hardware "fix" I could find. Then came a unexpected turn: I had given up and powered the desktop down with one difference - that time I also unplugged the AC power cord and left it off for a couple days. Upon turning the PC on again, lo and behold - the external drives (except one) appeared in Disk Management!
Don't ask me.
Of course, the Windows 10 "improvements" prevented them from being mounted automatically like in Windows 7/XP/Linux, they each had to be manually assigned a drive letter first. It remains to be seen whether or not the next W10 update (v-1703 Creators) will affect these problems.
The single exception to external drive recognition was a 3.5" enclosure model that was "updated" by the factory mid-production to "improve" (ha ha again!) the functionality of the HDD activity LED - apparently the changes also somehow prevent the W10 OS from detecting it via the eSATA connection no matter what you do, although its USB 3.0 connection still works, and that same eSATA connection works OK in Windows 7/XP/Linux.
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Sorry to be a wet blanket, but the run "Windows Memory Diagnostic" trick did not work for me - after trying everything else, I ran it twice, in standard mode and then extended mode, the last taking several hours. It had no effect, the external SATA drives still could not be detected at all (other than in BIOS), not in explorer, disk management, device manager, show hidden devices, or any combination of cables, enclosures, drives, driver updates, SATA ports, BIOS settings, and scanning for hardware changes.
The thing is, the various external hard drive enclosures are detected OK in this same machine (and others) with Linux, Windows XP, 7, and the first version of 10. If the drives are taken out of the enclosures and put in the PC's internal racks they work OK there too. It was only after running Windows Update to get Windows 10 V1607 (Anniversary with the latest Sept. 2017 updates) that the external drives could not be detected, either by hot-plugging or booting with the externals connected.
There are many similar complaints going back a long time posted on a lot of web sites, so it looks to be purely a Windows 10 problem which is being ignored by Microsoft. Those asking for help on Microsoft's support site seem to only get non-answers, such as try running the built-in hardware troubleshooting tool and posting the results. This seems to be a standard evasive reply, given out again and again, even though that tool only ends up saying "Troubleshooting couldn't identify the problem".
Anyone have suggestions? This defect and a lot of other well-known glitches/security leaks make Windows 10 an ongoing nightmare. Even Windows XP works better for most purposes, and Linux looks more and more like a savior.
Edited by DamnWndws10 - 10/1/17 at 12:03pm