Zooming in on the Win7 taskbar preview. You can see the

First, click the Start button, enter Regedit in the Run box and press Enter to open the Registry Editor.

Open the registry editor

and then go to the branch hkey_current_user/Software/Microsoft/Windows/CurrentVersion/Explorer/Taskband in the registry editor, in the blank space on the right side of the list Right click, select New - DWord value, and rename the key name to Minthumbzizepx.

New DWord Value

Double-click the newly created Minthumbsizepx key, and then enter the preview window size you want to adjust in the value data. The default is around 200, you can adjust to a slightly larger value, such as 300. Once set, click OK and close the registry.

Modify the Minthumbsizepx key value

Log out of the user, log in again to see the preview window becomes larger.