I have a Lenovo l512 laptop with a cracked screen which I acquired and installed Linux on. Thanks to the advice of TobiSGD I upgraded Debian to 6.0 (squeeze) and now have dual head in operation. I installed KDE to check out some of the candy it offered and while messing with the options I found something peculiar. When I turn on desktop effects using XRender for compositing (apparently OpenGL isn't working) and set my Monitor and LVDS to be clones, the crack shows itself as a distorted region on the monitor. I found this surprising and I wonder if anyone out there could enlighten me on why this artifact shows up, and if there is a way to resolve this without replacing the screen of the laptop?

You are welcome to look at eye candy.
It is unwise to run a cracked lcd screen, as the (unknown) faults may escalate. I take it the crack is appearing as a distorted area in the otherwise good monitors. That sounds very unhealthy. It suggests that high values (=visible information) are not being read as fully high, so the distortion becomes evident. That cracked screen is malignant.

If you don't want a new screen, arrange for the lcd to go off. Most laptops can use external monitors only. That's the way to go, my friend, while you still have a video card.

Wow, are you telling me that a cracked screen could actually damage the video hardware? I've never heard this before. If that is true maybe I will get a new screen for this thing after all.

Also, the artifact doesn't depend on LVDS being on, currently the laptop screen is off. The artifacts on the monitor only show up when KDE desktop effects are enabled (as in compositing active via XRender)

If you set up your monitor and the LVDS to be clones, aren't then both of them on?

Yeah they were, but after reading that warning I got scared and turned LVDS off, but the artifact remains.

Well, I'm a hardware guy, and I'm trying to think how the artifact could be passed from one monitor or screen to another. On a screen low voltage is black, high voltages show current. Digital is about lows and highs. On a 5V supply, 2.0 volts is guaranteed 'high' in value, as is 5V. I'm guessing you are seeing the difference between 2-4 volts (where the screen is broken) and 5Volts (elsewhere) in certain places as your 'artifact.' People will jump in and point out that monitors run on 0.7V, and not digital levels, and that is what really worries me - it's travelling back into your box some distance. I'm painting it dark in this scenario. It could equally well be bright if the screen is shorting outputs, but the effects on the system change very little.

So, something is probably being pulled down(= overloaded) somewhere, and I (as a hardware guy) am getting nervous. Screen cracks rarely improve.