How do I know if my DVD burner is connected to my computer?

How do I know if my DVD burner is connected to my computer because I have spent the last few days trying to figure out how to burn a Movie from my Pc to a blank DVD and it always says please insert a writable disc even though I just put in a disk that I had just opened. I have tried Nero and everything else imaginable but nothing has worked. what am I doing wrong?