The term "REPACK" in the context of software downloads is a red flag. It usually indicates that a piece of software has been re-packaged by a third party—often pirates or hackers—to bypass installation requirements or licensing checks.
When a developer writes code to "open an Excel file and read row 5," their program does not know how to talk to Excel natively. It needs a roadmap. The Object Library (specifically the file Microsoft.Office.Interop.Excel.dll ) provides that roadmap. Microsoft Excel 12.0 Object Library Dll Free REPACK
The answer is . Many corporations built massive VBA (Visual Basic for Applications) macros and VB6/.NET applications between 2007 and 2010. These applications hard-coded references to version 12.0. If you try to run them on a machine with Office 365 or Office 2019, you may receive the infamous error: The term "REPACK" in the context of software