The error message simply means you had no writeable disc in the CD/DVD drive. It is not connected to the other issue, which is most likely a failed backlight bulb.

If under warranty call Dell; they'll replace the screen. If out of warranty, contact an LCD repair shop, as it will cost $100-150 to replace the bulb, vs. 3-4X that to replace the panel.

It could be an inverted board. I've never had one fail before, so I'm not sure how dim screens get when they do go.