The related question was asked here, but the answer didn’t explain why this happens.
I directed the custom install to my D:\ but it ignored that and installed 500MB on the C:\ drive. Since the System drive is a scare resource, I want to install as little as possible there. As far as I remember with earlier versions, up until a few weeks ago, were installing to my D:\ drive.
So, why is this happening? Is there anyway to fix it?
The program is correctly installed in any folder/drive you specify. The problem is that the installer is packed into a single msi file and needs to temporarily be unpacked (all files are erased after a successful install). Since you probably are using the Windows defaults, your temporary folders are on the system drive (C:)
The solution is to move your temporary folders to your D: drive as well
Well, I did that, but no change, the installer still asks for a whole bunch on C
Can you upload a screenshot of a of those files/folders (use Treesize Free)?. If space is really an issue, then I recommend X-LibreOffice (a portable, self-contained version available at Office suites / Downloads :: winPenPack - The Portable Software Collection )
Can you upload a screenshot of a Treeview of those files? (use Treesize Free)