The single (MBR) HDD in this machine is partitioned for OS (dual boot) and data (multiple). I noticed in the context menu that the partition used to store software install packages has a Open Autoplay pick whereas the OS and Data partitions do not (as expected).
The 10 Boot (C: ) and 10 Data (D: ) partitions were created during/after a clean install of 10.1607.
The 05 swSetup (F: ) partition was created with 8.9600.
This really shouldn't matter, but it might be part and parcel of the other issues reported on drives marked raw or unallocated (not the case here though).
This doesn't seem to cause any issues, it's just odd to offer a Autoplay menu pick for a partition on the same internal HDD as the OS. I'll dig around a little to try an determine why Version 1607 (OS build 14393.187) thinks the partition is a removable drive, but I think this falls into Microsoft's domain to fix. I don't know when this oddity first appeared, I just happened to notice it when I went to run Defender on the drive for a routine scan (no malware suspected or found in the scan).
If anyone has a HDD with partitions on a drive that were created in Win8.1 being accessed by Win10.1607, could you check if your machine presents the Open Autoplay context menu pick for that partition?
Yes, I know the OS is on a logical drive, I've been running my systems this way for a long time. Only the SR has to be on a Primary partition, the rest can be Logical.