There has been a lot of discussions around the net on the non-customizable and non-removable Windows Vista startup sound. Robert Scoble has a post that explains why the Vista team decided to design it like that.
My personal opinion, like Roberts, is that I would like to decide for myself if I wan't a startup sound when I turn my computer on. For example; at home I have Windows XP Media Center which would benefit from having that sound, it lets me calibrate the volume before I put on a movie and it makes me aware of when the machine is up and running.
But when I'm on the road, especially on trains, or in areas where people get pissed if someone even whispers like lectures, seminars etc it is so embarrassing turning on a machine and have a high volume Tadaaaaa telling everyone that you just booted your computer.
On the Windows Vista Team Blog they justify and compares the sound to the startup sound of Xbox 360. We are talking about a device that you normally don't have with you on the road and when you fire it up you really want some nasty sound!
So - Vista guys - make it an option for us to turn the sound on or off.
On a side note the startup sound has been a pain in the ass for me. A few years back when I was running NT4 Workstation I could not get any kind of sound from it for the first few hours it was running, then suddenly the startup sound started and everything was fine...