One new feature of Windows 7 are thumbnail previews when hovering the mouse over a taskbar item. The default time before the thumbnail is displayed is 400 milliseconds which might be not fast enough for some users while it might be to fast for others. Here is how you change the Windows 7 taskbar hover time.
Load the Windows 7 registry editor by pressing [Windows R], typing [regedit] and hitting [enter]. Navigate to the following Registry key:
Locate the Registry key MouseHoverTime. It should have a default value of 400 (milliseconds). Simply double-click that entry and change the number. The thumbnail will appear faster if you enter a lower number or slower if you enter a higher one. You need to logout or restart the computer before the changes take effect.
The same menu contains several addition parameters of the mouse in Windows 7 including the double-click speed, mouse sensitivity or mouse speed.