Digital music store 7digital has announced that it's launching a Windows 8-based version -- and you can even shop around on the preview iteration, ahead of the operating system's October launch date. The store will offer up 20 million tracks, with your account still working across the existing platforms, including the recent Windows Phone version. This preview app, which runs on both the desktop and metro versions, also includes 7digital's music discovery service and 30-second previews of all its content. If you've
