[FIX]Windows 10 Anniversary Update error 0x80070057

Windows 10 Anniversary update is now available to general public as Explained here and on the community forums I saw a large number of people reporting 0X80070057 error while updating to the latest build using the upgrade assistant.I will discuss the solution in detail in this article.

Solution

Generally error code Anniversary update  0x80070057 signals corruption of Windows update files (Source) but looks like this isn’t the case here. On one of my computers, I noticed that the upgrade assistant tool is throwing this error by checking in the log files. So to get the Anniversary update, use an Alternate called Media Creation Tool, which is present on the same page of the Windows 10 Software download as shown:
You can use this direct link
 
After downloading the tool, accept the license terms and click Upgrade this PC now, Windows will automatically install the Anniversary update.
Personally, I find MCT more reliable than the upgrade assistant, as it also allows saving the Installation file if you want.
Questions? Feel free to comment!
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