1. Check for additional install errors
If there are additional error codes listed below the 0x800 error, note these and search the Sage Knowledgebase for the relevant solution.
If the issue persists, please continue to the next section.
2. Install directly from the installation files
Try installing Sage 50 Accounts directly from the installation files.
If the issue persists, please continue to the next section.
3. Uninstall and re-install .NET Framework
Please remove and reinstall the Microsoft .NET Frameworks starting with the latest version.
Typically this would mean removing Microsoft .NET Framework 4.5 / 4.6 or 4.7 then removing 3.5. You should then reinstall all versions starting with Microsoft .NET Framework 3.5. For help with this please speak to your local IT support.
If the problem persists the following Microsoft article gives more detail:
https://support.microsoft.com/en-gb/help/976982/net-framework-update-installation-error-0x80070643-or-0x643
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