1.go to control panel.
2.click the sounds & audio devices tab.
3.click on the sound you wish to change the sounds are available and labelled in the box on the lower half of the sounds control box.
4.click on the browse button in the bottom right corner of the box.
5.select your custom sound (sound file must be in .wav format)
6.press play button next to browse to confirm ur sound.
7.save the sound scheme by clicking save as & setting a unique name.
8.make sure that ur sound scheme is selected.
9.click apply & exit out the box.