There was a lot of controversy of the new Windows Start sound in Windows Vista. Originally, Microsoft was planning on making this a mandatory sound that users would not be able to disable.  This sounds like a great idea from a Marketing perspective since all Windows users world-wide would hear the same notes when their computer starts up.  However from a user perspective this could be a nightmare.  Thankfully Microsoft responded to the vocal Microsoft community and gave users the option to disable this sound. 

Follow these steps to disable your Windows startup sound:

1. Click on the Start Button and type in Sound.  Select Sound from the list.
2. Click on the Sounds tab.
3. Remove the check from Play Windows Startup sound.
4. Hit OK.

Enjoy.