If you are missing this library, you cannot simply download a single .dll from an official Microsoft page to fix it. Instead, you use one of the following methods: Microsoft Office 12.0 Object Library Filename and Location?
To understand the need for a download, one must first understand the technology. The Microsoft Office Excel Object Library is a Dynamic Link Library (DLL) that allows external programs to communicate with Excel. It acts as a translator. When you write code in C#, VB.NET, or legacy Visual Basic 6 that says Workbooks.Open() , your programming environment needs to know what a "Workbook" is and where the "Open" function lives. microsoft office excel 12.0 object library download