Let me put it to you this way: You know you pressed the power button on your computer, you know Windows is starting up, but does that necessarily mean you need an annoying sing-song chime to indicate that your machine has booted?
No, it doesn’t. So let’s learn how to make Windows 7 silent upon Startup!
Press Start, and in the Search Box type mmsys.cpl.
Now press Enter.
The sound dialog window should open up. Click the Sounds tab.
At the bottom you’ll see a checkbox that says “Play Windows Startup Sound”. Un-check it, and press OK.
Now Windows will keep its yapper shut when it boots up! If you want the sound back, just follow these steps and re-check the box!