Highly irratating alert tone.

Hi All:

I have a w7 computor that is driving me nuts with the regular sound tone being emitted every minute or two.
To illustrate when a USB is plugged it is searched to install and when found gives out an alert tone to say it is connected That is fine. Likewise when removed the same sound is emited. fine. But this is much louder and never stops - it goes on and on

what is causing it and how can i disable the damn thing!!!!!!!!!!!!!!

Thanks alpacapete