Error Code: 0x80070643 (Windows Defender can't install definition updates)
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Windows Update error 80070643 can happen for several reasons. The most common cause is a problem with the .NET Framework installed on the computer.
The .NET framework is a part of Windows that's used to build, deploy, and run programs and applications. Unfortunately, it can be damaged by some programs, viruses, or hard disk problems.
To repair the .NET Framework automatically-
Click on the below link
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