I just stumbled upon the file to the "Galaxy S" and Verizon Power On Chime. It's all in one file. It's located in /system/etc/ as PowerOn.wav. It is currently 8 seconds long. You can replace that with any .wav to change the sound, BUT, I'm not sure how long it will play a chime. Like I said, it's 8 seconds, and it controls BOTH the Galaxy S and Verizon Startup "Theme Song". You may make a .wav file that is silent so there will be no sound at all.