Someone

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;

namespace MinimizeAll
{

    public partial class Form1 : Form
    {
        [DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Auto)]
        static extern int GetWindowText(IntPtr hWnd, [Out] StringBuilder lpString, int nMaxCount);

        // This static method is required because legacy OSes do not support
        // GetWindowLongPtr
        public static IntPtr GetWindowLongPtr(IntPtr hWnd, int nIndex)
        {
            if (IntPtr.Size == 8)
                return GetWindowLongPtr64(hWnd, nIndex);
            else
                return new IntPtr(GetWindowLong32(hWnd, nIndex));
        }

        [DllImport("user32.dll", EntryPoint = "GetWindowLong")]
        private static extern int GetWindowLong32(IntPtr hWnd, int nIndex);

        [DllImport("user32.dll", EntryPoint = "GetWindowLongPtr")]
        private static extern IntPtr GetWindowLongPtr64(IntPtr hWnd, int nIndex);


        public delegate bool EnumDelegate(IntPtr hWnd);

        [DllImport("user32.dll")]
        static extern bool CloseWindow(IntPtr hWnd);

        [DllImport("user32.dll")]
        static extern bool IsWindowVisible(IntPtr hWnd);

        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        static extern bool EnumDesktopWindows(IntPtr hDesktop, EnumDelegate lpEnumCallbackFunction, IntPtr lParam);
    
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            EnumDesktopWindows(IntPtr.Zero, delegate(IntPtr win)
            {  //filter the windows:
                if ((GetWindowLongPtr(win, -20).ToInt32() & 0x00000080) > 0)
                {
                    //tool window
                }
                else if (!IsWindowVisible(win))
                {
                    //window not visible
                }
                else
                {
                    //maybe....
                    StringBuilder sb = new StringBuilder();
                    GetWindowText(win, sb, 100);
                    if (sb.Length > 0)
                    {
                        CloseWindow(win);
                    }
                }
                return true;
            }, IntPtr.Zero);

        }
    }
}