[InterceptPoint]

The subdirectories that hold upgrade files are probably damaged. At least it finally upgraded.
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What would cause that? Errors in the download process?

[Calvin Locke]

No idea, but when I upgraded my 8/8.1 to 10, I had the problem, and deleted the subdirectories, rebooted, and check for updates to install Win10. I don't think I've had any issues with either of the two Win10 machines I have (desktop/laptop).

My mother's pc has an "update failed" problem about every other update. It was originally running Win7. Deleting the directories has solved issue each time.

Can't remember if I blew away all the subdirectories away in the download subdirectory, or just the ones with the update date.