I'm using Visual Studio 2008 and the imported GeckoFX-Framework in one of my projects. Since the Geckofx-13.0.dll uses the XUL-Runner itself, it's mandatory to have those files also in the build-directories of the project. Up to now I used to copy them manually into the two directories (Debug & Release).
I'm asking myself if I could tell VS to copy them automatically into those directories.
If those files are missing, the execution of the build fails.
You could add the required files to your project, set them as "Content" in the properties window and set the Build Action to "Copy if Newer".
You could add a Post-Build action (right-click project, choose properties) to the release and debug configuration to copy the files to the output directory (you can use a macro instead of hard coding, that way the right destination is always used, also when it is edited in the project settings). A simple copy .\Files\*.* $(TargetDir) would probably work. Any command you can execute from the command line works here as well.
The preferred way:
You could add a Post-Build target (right-click project, unload project, rightclick unloaded project, edit project) and use the msbuild <copy> tasks to copy files from one location to another. You can again use a macro such as $(OutDir) or $(TargetDir) or $(Platform) and $(Configuration).