I had taken the following action based on R. Profitt's "I haven't read a solid answer on this beyond" after writing the post "Thank you" but before reading all answers up to Oldartq's "Ok, lets "skip" all I have said before"--
Win 10 32-bit (my opening post) had been upgraded from existing Win 7 Home 32-bit using Windows Update and the process was smooth and had succeeded in first attempt.
On 2nd hard disk of the same computer---blank, wiped using CCleaner Drive Wiper entire drive 1 pass, formatted, new volume created, drive letter assigned---made a clean install for Win 10 using USB drive---downloaded shortly after July 29 release.
Clicked the skip button, when asked, and the installation began smoothly, and ended without a hiccup. When the system booted, I opted for boot from the 2nd hard disk, where the new installation had recently been made.
However, system booted from 1st hard disk where 32-bit version had been upgraded earlier. Twice more, I attempted reboot, ensuring I asked for boot from the 2nd hard disk but, every time, system booted only from 1st hard disk.
Noticed that space occupied on 2nd hard disk was very small, contained PerfLogs, only one folder for Program Files, only one folder for users (Public), Windows, and Windows.old (empty).
On 2nd reboot attempt from the 2nd drive, space occupied grew only by 1 GB. On 3rd reboot attempt, space occupied grew by a couple of GBs---finally 13 GB---contained a 2nd folder for Program Files, but no 2nd folder for users (my folder).
For reasons not quite understood by me, folder additions and increase in occupied space took place one by one in each successive reboot attempt from new clean installation, a phenomenon which I had not witnessed any time during any of my prior installations on 3 PCs, mostly clean installs of Windows XP Pro, Vista, Win 7, and Win 8.1, all OEM versions, all 32-bit, except 8.1 64-bit.
Now, I am thinking of a clean install of Win 8.1 x64 on 2nd hard disk, and then an upgrade to Win 10 via Windows Update, and see what happens.
Any more thoughts would be welcome!