Dave writes, "I have an old PowerBook G4 laptop with a broken monitor (it just displays vertical lines). I connected it to my HDTV using an HDMI cable and a DVI to HDMI adapter and all I got on my TV was a blue screen. I had the TV set to the right input. Any ideas?"
Connecting an external display to a MacBook or PowerBook, as you did when you connected your HDTV, typically causes the Mac to extend the desktop to the external display. Sometimes this doesn't happen automatically, which means you need to make manual changes. In your case, the Mac shouldn't try to use the built-in laptop screen because it's broken, but the Mac probably can't detect that. Fortunately there's a relatively simply solution to the external display problem you are having.