One can achieve to minimize all open windows in many ways without using the Windows key. On a computer, try pressing Alt + Tab ↹ to minimize each window individually, or use the taskbar buttons to minimize all open windows at once.
Steps
Method 1 of 3: Use the taskbar to access the desktop

Step 1. Right click on the task bar
The taskbar is the bar at the bottom of the screen where you can access and view the programs. When you right-click there, a small window with options should appear.

Step 2. Click on the "Show desktop" option
This way you should minimize all open windows and see the desktop.

Step 3. Right click again to reset your window and view it
Find the option "Show open windows" in order to maximize the active windows again.
Method 2 of 3: Use the "Show Desktop" button

Step 1. Hover over the right corner of the taskbar
In recent versions of Windows there is a rectangular button in the lower right corner of the taskbar that will be "hidden" until you click there.

Step 2. Click on this "hidden" button
The button will appear opaque once you click and will minimize all currently open windows.

Step 3. Reset all windows
If you want to maximize the windows that you minimized earlier, click the rectangular button again. This will maximize all the windows that you minimized.
Method 3 of 3: Use a command on the keyboard

Step 1. Click on an open window that you want to minimize

Step 2. Use Alt + Tab ↹ to minimize

Step 3. Click on another window to select it
To keep minimizing all open windows, select each window one by one and repeat the Alt + Tab ↹ command until all are minimized.

Step 4. Restore a minimized window with Alt + Tab ↹
To maximize the window you just minimized, use Alt + Tab ↹ before selecting a new window.
The Alt + Tab ↹ command only works to minimize or maximize one window at a time
Advice
- On a Mac, the ⌘ Command + ⌥ Option + M buttons hide the currently active window.
- On a Mac, the ⌘ Command + ⌥ Option + H buttons hide all windows except the currently active window.
- On a Mac, the ⌘ Command + ⌥ Option + H + M buttons perform both of the above functions and minimize all windows.
- If you have Windows via Remote Desktop on a Mac, the Alt + ⇞ Page Up buttons will only minimize windows on the remote desktop; while Alt + Tab ↹ buttons will only minimize windows in local interface (main computer).