Well, this is a very late response but I saw my defunct laptop sitting there and decided to give it another go.
Long story short -
SOLVED!
Before this last try at it, its status was as I said in post #23:
Unable to boot, error 0xc0000428
Gregrocker, I believed I had followed all the instructions in
Startup Repair - Run up to 3 Separate Times. According to one of my previous posts
(here, post #10) I had checked to see if the correct partition was active and it definitely WAS then, as per the screenshots in that post. I had run Startup Repair 3 times with restarts in between, many times.
Anyway, I followed your second link to
Mark Partition Active and decided to mark the correct partition again. From the previous screenshots
(here, again - post #10) you can see that Partition 2 was active. But I set Partition 2 to be active again anyway, and my next reboot succeeded.
I've attached a screenshot of my
working computer's current output from diskpart. To me it appears that the same partition is active now (and it works) as was active back in post #10 (when it didn't work). If you can find any discrepancies, please let me know! I'm not sure at all why my latest actions worked, since I don't think they changed anything. Perhaps there was some action I took between post #10 and now that cleared the original issue but marked the incorrect active partition. I unfortunately did not look at the active partition immediately before re-declaring partition 2 as active again.
But I would like to once again say THANK YOU to all who contributed to this thread. All contributions were helpful and I learned a lot about the various stages of Windows' boot process. I hope that this thread will help someone else in the future.