Aero peek : A feature in Windows 7 which makes all open windows transparent when mouse is hovered over the little rectangle in bottom right.
Here is how to disable Aero Peek :
* Open Run Dialog (Press Winkey + R).
*Move To : HKEY_CURRENT_USER\Software\Microsoft\Windows\DWM.
*In Right Side Pane Double Click on "Enable Aero Peek" as in above image.
*Type Value As 0.
*Aero Peek Is Disabled.
Download the registry file to do this for u