Minimize one, single window in Windows 7 with keyboard shortcut

Using the Windows Key + Down Arrow.

Update: If the window is Maximized, it will first go "Un-maximized" then a second Win + Down Arrow will Minimize.

Here is a link to all of the Windows Key Shortcuts available in Windows 7.

Edit (new link): https://support.microsoft.com/en-us/help/12445/windows-keyboard-shortcuts

(for reference this was the old link): http://windows.microsoft.com/en-US/windows7/Keyboard-shortcuts

Minimizing single window is not possible via simple shortcut. However, you can use combination of two shortcuts Alt+Space followed by letter N.

Pressing Alt+Space opens the context menu for the current window and the keyboard mapping of the Minimize option is 'n'.