Well, it seems that in my case, it was someone else logging into my computer and using gtalk! Specifically, my girlfriend had logged in as a guest and left her gmail open. She then switched users back to my account and left. Later, she got on gmail on her laptop and began chatting. Her gtalk...
I am also experiencing this annoying issue. In my case, it is the same sound that is played when I get a message via gtalk when I have my gmail open, NOT a sound in the C:/windows/media folder. Could you pin-point what sound you are hearing? Obviously, I wouldn't be posting here if the source...