Just a short tip for those about to install Mac OS X 10.6 Snow Leopard. When you insert the DVD to install 10.6, the installer does something a little different than previous installers -- it pre-installs a bunch of stuff onto the 10.4/10.5 machine before it reboots with the DVD to finish the installation. I guess this is done to speed up the installation.
Anyhow, during this process, do not be tempted to turn down the brightness of your screen while this is happening. I did that, and when the machine rebooted from the DVD, the brightness of the screen was turned down to zero and I couldn't see anything.
So, do not turn down the brightness, even one above zero (which is what I did), or you will be faced with a black screen because the brightness keys do not work in the installer boot. Fortunately, I had another drive with an installation that was able to boot my Mac, and I turned up the brightness and rebooted again to continue with the installation.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20090827114143750