One of the small but annoying things in Windows Vista is the fact that the System Beep is enabled by default. Every time you encounter an error or you click through the menus of applications such as the AVG antivirus, you will hear a beep. In the beginning you might ignore it but after a while it becomes very annoying.
For those of you who want to get rid of the beep, in this tutorial we will show how to disable it.
First, go to your desktop and right click on the My Computer icon. From the drop-down menu select Manage.
In the Computer Management window go to System Tools -> Device Manager. If UAC is turned on, you will need to make some additional confirmations in order to access the list of devices.
Now you will need to go to the View menu and select Show hidden devices.
If you return to the Device Manager you will see a category of devices called Non-Plug and Play Drivers. Expand that list and select the Beep, as shown in the screenshot below.
Right click on the Beep and select Properties.
In the Beep Properties window go to the Driver tab. From the Startup scroll down list, select Disabled and press OK.
At the next restart, the Windows Vista System Beep will be disabled.
Source Site: Windows Vista for Beginners - Windows Vista tutorials
Source Article: Disable the System Beep