Annoying windows guitar sound?

A really annoying and disturbing sound is coming from my computer all the time and I have no idea, why. It's nothing like one of the 'Windows sounds', more like aggressive and energetic, tasteless guitar music, a small fragment of it. It just keeps repeating after every 2-3 minutes and makes it impossible to listen to the music, which makes me very pissed off and unproductive employee, and surely that will lead to global crisis. It's office's computer, I checked for any previously downloaded pop-ups or opened programs or something like that, and could find nothing. Anybody has a clue? Would be extremely appreciated.