Did Windows 10 installer just overwrite my data drive boot partition?
It certainly looks like it:
Now, this is quite alarming, because originally, I had Disk1 Partition0 as my System/Boot partition, and my Disc0 as my data partition. Despite this, when I installed Windows, it seemed to select Disk0 for the System (boot.ini, etc) partition.
The reason it’s alarming, was that Disk0 was whole-volume encrypted using Truecrypt. If the Win10 installer has overwritten the start of the disk with new boot files, it has likely destroyed critical sectors of the Truecrypt volume and made my whole data drive unusable.
Luckily I have a backup, but this is still a rude shock. I guess I might have missed this when preparing the disk at the start of the Win10 installation, which I did play with. If so, then it’s something to look out for yourself.