Desktop preview with Aero Peek is a new Windows 7 feature. Hover your mouse cursor over the bottom right hand corner of the screen and Windows 7 will hide open windows, showing you the desktop. It is a very useful feature, but if you don’t think so, you can simply turn it off, by following a few steps:
1. Right-click the Start orb
2. Select Properties, clik on Taskbar tab
3. uncheck the “Use Aero Peek to preview the desktop” box.