In Windows 7 we can see the Thumbnails of the Windows when we hover our mouse over them in the Windows 7 Taskbar. This is a really cool feature of Windows 7. But it takes a small time interval to get the thumbnail appeared. We can reduce it and make the Thumbnails to show up Instantly when we hover our mouse over it. Here is what you have to do.
Press [Win] + [R] or select the RUN option in the Windows 7 Start Menu.
Type regedit and press [ENTER].
Navigate to HKEY_CURRENT_USERControl PanelMouse.
Look for the key MouseHoverTime and double click on it.
And Enter 0 as the Value Data.
Now close the registry editor and restart your system. You can see the Thumbnails in the Taskbar are showing up instantly.