The only way to change any of the start up stuff is with an illegally acquired program that is not for public use. You can do some serious damage to the device if you don't know what you are doing.
Don't ask for the name of the program either, as I don't think that discussion about it allowed here.
Odd. I have a Verizon BB Tour and it does not make any startup sounds, ever. I have a Verizon BB Tour. I have had it for six months. I just pulled the battery to try and get your sound and never got it.
I have a feeling that the sounds at start up may be related to OS, I have my sound effects to on since I got mine and mine makes no sounds at all when it starts.