A suggestion from Apple to remove and then re-install the video card seemed to work to fix the problem with a black screen when booting.
Zap the Pram and see if that helps also.
Some sound files are here and can be changed;
System/Library/Components/CoreAudio.component(Right click or Control click for Package Contents)/Contents/Resources/SystemSounds
The Startup sound is on the Logic Board.
Check SystemSound to change that.
After the password entry then press ENTER. THEN Type in "logout" exactly like that without the quotations then press ENTER! Then it should take you back to Tiger/Panther/Whatever OS X you use.