Line in Screen showed up

I have an HP {avilion TouchSmart 23 All-In-One and I am now the proud owner of a green line down the side of my screen. It sits some 2 1/4 inches off the left side and seems to want to stay with me. However, as this was a pretty expensive model, I'm not so sure I want this to remain with me.

Who do I contact to make this go away? Should be under warranty as it's less than a year old - in fact, less than six months.

Thanks ever so, TipperTop