É o Shake da Janela. Se você mover uma janela de um lado para outro, isso minimiza todos os outros Windows.
Para desativar: Do How-To Geek.
Disable Aero Shake Manual Registry Hack
Open up regedit.exe through the start menu search or run box, and then navigate down to the following key:
HKEY_CURRENT_USER\Software\Policies\Microsoft\Windows
Once you are there, right-click on the Windows key and create a new key called Explorer.
Now right-click on the right-hand side, create a new 32-bit DWORD with the following settings:
Name: NoWindowMinimizingShortcuts Value: 1
Once you’ve created this, you should log off and back on for the change to take effect.