Starting with Windows 7, taskbar started displaying thumbnail preview of opened program when you hover over icons. Multiple preview windows are displayed in case of multiple instances of programs are opened.
Disable Taskbar Preview with Registry Editor
In case you want to Disable Taskbar Preview, you will need to modify Windows registry with its registry editor. unfortunately there is no method of disabling it permanently, what you can do is to increase the delay time for Taskbar thumbnail to pop-up.
- Press the Windows-key or click on Cortana search box, type regedit.exe and hit enter.
- Windows may display an UAC prompt which you need to accept before you continue.
- In Registry editor navigate to the key HKEY_CURRENT_USER\Software\ Microsoft\Windows\CurrentVersion\Explorer\Advanced.
- Search for Dword ExtendedUIHoverTime on the right and double-click on it. If it is not available then you should create one yourself
- Change the value to a very large value like 10000 or bigger (1000 = 1 sec.).
- Close registry editor and restart the PC for change to come in effect.