If you are using an older version of Office and need to interact with Excel 2007 formats/libraries, ensure you have the official Compatibility Packs installed from Microsoft’s official archives.
Downloading "repacked" DLL files like the Microsoft Excel 12.0 Object Library from unofficial third-party sites is strongly discouraged microsoft excel 120 object library dll free download repack
In a standard installation, this library is often housed within EXCEL.EXE (e.g., in C:\Program Files (x86)\Microsoft Office\Office12\EXCEL.EXE ) or may be referenced as MSO.DLL for broader Office functions. The Dangers of "Repacks" and Unofficial Downloads If you are using an older version of