Windows 7 has provided a cool feature with ability to preview taskbar thumbnails whenever the mouse is hovered on the program icon. However, you may notice that it does have some latency to display the preview after mouse over the icon. To speed up the thumbnails preview, you can change the delay time with simple steps.

The delay time can be change via registry key. Please follow below steps to change it:

1. Go to Start -> Run, then type regedit.

2. Navigate to HKEY_CURRENT_USER\Control Panel\Mouse.

3. On the right panel, look for MouseHoverTime and double click on it. Change the value to 0 (in millisecond) then click OK button to save the changes.

4. Close the registry editor and restart your computer in order to take the effect of the changes.

Once you have completed above steps, you can verify the delay time taken to display the thumbnail preview if it is faster than the previous.