The DocumentFormat.OpenXml.dll is registered in the GAC when the SDK is installed so it doesn't physically copy it to your project's output folder by default when you build the application. If you select the option to Show All Files in Visual Studio (Project | Show All Files), you'll see a References node appear in your VB.NET project in the Solution Explorer. Expand it, select DocumentFormat.OpenXml, view it's properties, and set the Copy Local option to True so that it copies it to the output folder when you build the app. You can then copy it along with the app to any other PC and it will run without having to install the SDK on them.