Okay well let's try something else. Sometimes it's a bizarre permissions game M/S plays. You guessed it, since Win 7 is EOL don't expect M/S to fix it.
Try this: Make sure you are logged in as administrator, download the stand alone version from M/S catalog and run it (as administrator) and see if that works. Evidently it installs fine, the problem is with clean up and permissions needed to do so. Try that and see if it works. How many O/S are you booting from the drive that has Win 7 installed? That has been a problem with this update as well but let's not get ahead of ourselves.
Edit:
Just to elaborate I have read that some undisclosed Win 7 set-ups refuse to clean up properly after attempting to install this update and go through the rollback sequence. Many people far more knowledgeable than me have stated this is a bug with the update itself. Since Windows 7 is EOL M/S refuses to address the issue. I remember encountering it on a couple of Win 7 installs post Win 7 EOL and saying to myself, oh well. If it's that big a deal to you move up to Win 10. I haven't done any post Win 7 EOL paid updates to any systems yet. I was not at my computer lab this week but it's on the to do list for next week. I'll report back if I find out anything else.