My computer makes a sound like poker chips randomly, why?

[blakepotatoe]

Hello, I am running vista and my computer just randomly makes a noise like poker chips being thrown into the pot. It especially does it when i am is not using it.

 

[ex_bubblehead]

You may be infected with malware.

Download, install, & run a full scan with Malwarebytes (http://www.malwarebytes.org/)

 

[blakepotatoe]

i have paid version and ran it, it found nothing.