Sometimes, the sounds in Windows Vista are really annoying especially when you are working and something pops up like a critical error or something. You can change or disable them in few easy steps mentioned below:

1. First of all, Right Click on your Desktop and click Personalize.

2. When the Personalization Window opens, select Sounds.

3.  If you want to disable all sounds, select No Sounds from Sound Scheme and it will disable all Windows Vista sounds.

If you want to change a specific sound, just select the program and change/disable the sound.

I hope that helped.