disconnect sound when running windows 7 on macbook pro 15"

First of all, here are some of my computer specifications:

Using macbook pro 15"

Mountain Lion OS X

Windows 7

When I use windows 7, I occasionally here the disconnect sound as if I'm removing something from the USB port. This happened more frequently this evening when I switched from using the mac operating system to the windows operating system using bootcamp. I have had my computer for a month, and this has just recently started happening. I have run upgrades for both the mac side and the windows side on the 24th of October. I take good care of my computer and have not done anything to cause harm to the USB ports. Please help.