Curiouser and curiouser!
I couldn't find a way to prevent Win7 doing its 'Important Updates' thang automatically, but... the whole shebang seems to have righted itself, second time around!
Win7 starts up in Normal Mode as expected, with the 'desktop image + icons + widgets + taskbar' combo appearing as indeed they should, in contradistinction to the Big Black Blank Screen of nothingness which appeared prior to Win7's second stab at installing those 22 'important updates' noted above.
The 'Windows Update' control panel now only shows the two optional updates, and I'm not going to the added time expense of matching the top 22 records in its 'Review your update history' table with the 'Chief Suspects' screenshot above - it just seems fair to assume that, on its second attempt at installing these 22 'important updates', Win7 succeeded where it had previously failed.
I was planning on putting IE10 in place, so many thanks for the link to its download page - it's now installed and seems to be running fine.
Goodness knows what went right this time cf. what went wrong last time, but I'm just fine about not looking this particular gift horse in the mouth. My inner mythology lover is wont to offer the explanation that a malicious and mischievous Pack of Gremlins tried messing up my Win7 partition, but once they saw I'd brought in Malware Analyst Gunslinger EssexBoy to straighten things out, the cowardly little minxes fled to a less well protected PC elsewhere. Pure and utter nonsense, I know, but as good a story as any!
So thanks for looking mean and dangerous and intimidating the WRONGNESS into going vamoosh at the hurry up - I really appreciate your assistance. Here's hoping it'll continue to be uninfected plain-sailing from this point onwards.