Move your mouse cursor over a Windows 7 taskbar button and you'll see a small preview of the application window. To make this larger, launch REGEDIT, browse to HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Taskband, right-click in the right hand pane and create a new DWORD value called MinThumbSizePx. Double-click this, choose the Decimal option, set the value to 350 and reboot to see the results. Tweak the value again to fine-tune the results, or delete it to return to the default thumbnail size.
