Steps to clean the Software Distribution Folder to fix Download error - 0x80070643

Press Windows + E to open the File Explorer. Press Ctrl + L and type %systemroot%\SoftwareDistribution in the Address bar. Now the SoftwareDistribution folder will open, which contains Download and DataStore folders. Open both of the folders and delete their content. Reboot your system, and now your Windows Update will be complete without any errors.