Modify the Microsoft Office setup to install primary interop assemblies for Excel

If you did not install .NET Framework before you installed the Office system, the PIAs are not installed with your Office installation. If you installed .NET Framework after you installed the Office system, you can install the PIAs by modifying the Office setup.

Before you begin

The Microsoft Office PIAs are installed in the global assembly cache in drive:/WINDOWS/assembly or drive:/WINNT/assembly.

You must be an administrator on the computer to install the .NET Framework and the Microsoft Office PIAs.


  1. From the Start menu, click Control Panel, and then click Programs and Features.
  2. In the list of programs, click the Microsoft Office version, and then click Change.
  3. In the Microsoft Office Setup wizard, select Add or Remove Features, and then click Continue.
  4. In the Installation Options page, expand Microsoft Excel.
  5. Click the symbol next to the .Net Programmability Support feature, and then click Run from my computer.
  6. Click Continue.
  7. Click Close.