Edit Time For a Thumbnail to Expand From Taskbar in Windows 7
As you can edit the time for the thumbnail preview to be shown from the taskbar, you can also edit the time for it to expand from hovering the cursor over it with the Windows 7 registry editor. To accomplish that enter regedit into a Run… prompt and browse for the Computer\HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced key on the left column of the editor. On the right panel, right-click to create a new DWORD-Value (32-bit) and call it ThumbnailLivePreviewHoverTime.
Assign it a decimal number that represents the time to expand in milliseconds (1000 units=1second) – I chose 100 here, so thats the tenth part of a second.