There can be many problems that can make YouTube Video Downloader unavailable. I recently installed this application on my computer and it worked just fine. Therefore I recommend you reinstall this application, but first you need to properly uninstall it. Go to Control Panel > Uninstall a program or you can use the help of an uninstalling application to remove all data that this application installed on your computer. After that go to the Software Informer application's page or its official webpage and start the download. Then, open the setup file and start the installation process once again.