This is a bit dated but it's worth mentioning anyway now that Vista is officially launched for businesses. Each major release of Windows comes with a startup sound. Vista is no different. It has a sound created by Robert Fripp. I was lucky enough to be able to attend one of the recording sessions for the new sound. Scoble captured that session and it is availabe at channel9.
The person responsible for the Vista sound is Steve Ball who happens to be a program manager in my group and sits just down the hall. He recently gave an interview to NPR where he introduces the new sound. It is short at just over 2 minutes and goes over the various sounds from past versions as well as the new one. Here is an article talking about the new sound.
Update: In the spirit of accuracy, the session I point to above is not the one that I attended, but is one like it.