Windows 7 task bar is also known as the super bar and offers cool features like larger icons, jump lists, pinning option and particularly improved thumbnail preview feature. Taskbar’s thumbnail preview displays a small thumbnail preview of your minimized window or application when the mouse is hovered over it. But usually it takes some time to display the thumbnail, to reduce this time follow the steps below.
You will need to edit some settings in the registry, go to Start, type regedit and then press Enter.
Now, navigate to HKEY_CURRENT_USER > Control Panel > Mouse in the left pan of the Registry Editor and locate the MouseHoverTime key in the main window.
Double click it, you will see that its default value is set to 400, change it to any value below 400, but make sure that it should not be less than 100. Since these numbers represent delay time, the lesser the better, so setting it to 150 will give you faster preview then 350.
Click OK and thats all, the task bar’s thumbnail preview will load faster then before. Enjoy!