If you previously uninstalled an older Office suite but left behind registry entries pointing to shared components, Windows may still look for the v90 Common Tools during Windows Update or system maintenance.
In 2021, the landscape of Microsoft Office shifted significantly with the release of Office 2021 and the continued expansion of Microsoft 365. One might assume that a version 9.0 tool would be obsolete; however, Microsoft maintains a strict policy of backward compatibility for the VSTO runtime. Developers often include these DLLs directly within their application folders to ensure that even users on the latest hardware can run specialized tools without a full re-installation of legacy development environments. microsoftofficetoolscommonv90 download 2021