When you open a folder in Windows Explorer a click sound is played. To disable this there are two ways to do it:

• Turn it off using the control panel:
  1. Open “Start”->”Settings”->”Control Panel”
  2. Open up “Sounds and Audio Devices”
  3. Open the tab that says “Sounds”
  4. Scroll down until you find “Windows Explorer”->”Start Navigation”
  5. When you mark this line at the bottom there is a drop down that is labeled “Sounds:” Here you should be able to change to anther sound or “none” if you do not wish a click.
• The second option is a bit more direct and rude – but if the above does not work for you (for me something kept resetting the old sound); just remove the file that contains the click sound.
  1. Open up a Windows Explorer and go to “%windir%\Media” and find the file that is named “Windows XP Start.wav”
  2. Either remove it (permanently) or rename it to something that windows won’t recognize (but you can – so you later can reverse this if you would like to)