Hello all, My hp envy 14-k008tx sleekbook has windows 8.1 pro. It doesn't have DVD drive. When I put Windows 7 ultimate to install and click on "Install now" button, it gives me an error saying "A required cd/dvd drive device driver is missing. If you have driver floppy disk, Cd, DVD, or USB, please insert it now. Note: If the Windows installation media is in the cd/dvd drive, you can safely remove it for this step." I don't know how to install that 7 on it. Any help will be appreciated.