21st February 2017, 18:25
Tower is now back in business 
It was my unintended usage of nomodeset in grub that limited the screen resolution. Now it's all good again.
If my stuff-up of the attempted kernel 4.9.9 removal did not cause the last several hours of terror, then i have to assume it was the apparently unsuccessful initial attempt to change from the nvidia to intel gpu driver that did cause it. As i wrote a couple of hours ago, after making that initial attempt, it was not at all clear to me that it had succeeded... & IMO, if it had succeeded, i would not have got that boot black screen, which was why i had to then use nomodeset. Later, indeed only within the past 45', when my 2nd attempt to invoke the intel driver did work*, i'd temporarily forgotten i had to remove nomodeset again [& now i've learned how horrible the res becomes as a result].
*I assume those hanging splash-screens were coz at that stage neither nvidia or intel gpu drivers were properly activated.
Does that post-mortem seem reasonable?
leszek & rocky -- i'm sooooooo grateful to you both, again, for rescuing me. I wish i could buy you a beer / scotch / milk / mineral water.
This is my last post in this thread to be made from Lappy, now that Tower is running again. Next post will be my last for the night [tis now 3.15AM here, yawn], will be back on Tower, & will show you some pics for your thoughts / confirmation of what gpu driver is actually active now.
It was my unintended usage of nomodeset in grub that limited the screen resolution. Now it's all good again.
If my stuff-up of the attempted kernel 4.9.9 removal did not cause the last several hours of terror, then i have to assume it was the apparently unsuccessful initial attempt to change from the nvidia to intel gpu driver that did cause it. As i wrote a couple of hours ago, after making that initial attempt, it was not at all clear to me that it had succeeded... & IMO, if it had succeeded, i would not have got that boot black screen, which was why i had to then use nomodeset. Later, indeed only within the past 45', when my 2nd attempt to invoke the intel driver did work*, i'd temporarily forgotten i had to remove nomodeset again [& now i've learned how horrible the res becomes as a result].
*I assume those hanging splash-screens were coz at that stage neither nvidia or intel gpu drivers were properly activated.
Does that post-mortem seem reasonable?
leszek & rocky -- i'm sooooooo grateful to you both, again, for rescuing me. I wish i could buy you a beer / scotch / milk / mineral water.
This is my last post in this thread to be made from Lappy, now that Tower is running again. Next post will be my last for the night [tis now 3.15AM here, yawn], will be back on Tower, & will show you some pics for your thoughts / confirmation of what gpu driver is actually active now.