Congratulations, it worked out. I really appreciate your help.
If you want the FixLog.txt at this point let me know.
Not only could I install the KB4534310, but also other optional KBs and other important ones that came out with additional checking.
Some side notes:
1) Before step 2 (but after rebooting), I checked my list of services and BITS wasn't running. I turned it on and restarted the PC again. I don't know if it was part of the problem.
2) The tool FRST64.exe performs a check when you start it and probably updates something. It would be useful to know what type of checks it performs.
Some questions:
3) The COMPONENTS file was a binary one. How could you read it? Is there a tool?
4) What was the problem in my case?
5) I have another VM with Win7 with similar problems but different KBs and I would like save you and the forum from the burdle to fix it. How could I perform alone the steps you did?
6) I have an ISO of Win7 and I followed the usual steps installing it and tried to update as many KBs as were available. I know that Win7 has reached its end of life support. At the beginning, when I checked Windows Update the first time it didn' work and I had to follow some instructions on the net installing at some particular KBs before using Windows Update properly. It seemed Microsoft has changed something in the "stack of SHA.." or something like that.
In a few words, when I have to install Win7 nowadays, which steps do I have to follow? Is there a guide on the net?
Thank you.