That yellow speaker in the lower-right of the screen (in the System Tray), allows you to display the volume control by clicking on it. To get rid of it:
- Right-click the speaker icon and choose Adjust Audio Properties from the menu
- At the bottom of the Audio Properties window, there’s a checkbox marked Show volume control on the taskbar; uncheck the checkmark will remove the icon from the tray.
If you need to restore the icon:
- Click Start > Settings > Control Panel
- Double-click the Multimedia icon
- On the Audio tab, put a checkmark in the Show volume control on the taskbar box.