You can change "Tap" sound to your own WAVE file. At first, you need to make sure you have Wavclick.dll on your image("\Windows"). if you do have the file, you can change "tap" and "keyboard click" sound.
Here are the files Wavclick driver plays. "TCHSOFT.WAV" - Soft Sound for Tapping Touch Screen "TCHLOUD.WAV" - Loud Sound for Tapping Touch Screen "KEYSOFT.WAV" - Soft Sound for Click keyboard "KEYLOUD.WAV" - Loud Sound for Click keyboard