If you do not have the library, you need an Office 2007 installer.
Since you cannot get a standalone file, you must install the source application that includes the library. Here are the three legitimate methods to obtain the Microsoft Office Excel 12.0 Object Library. microsoft office excel 12.0 object library download
If your project absolutely requires the 12.0 reference (e.g., maintaining a legacy VB6 application on a dedicated server), you must install Microsoft Office 2007 on that machine. If you do not have the library, you