How can I stop a liked hotkey from opening another instance?

[sourcez]

Ok so I've got an application which has a main form (MainForm) which can be started with a hotkey (currently Alt + print screen). My problem is that whenever the hotkey is called a new instance is opened...so another MainForm - I don't want or need two!

Is there some way I can simply minimise and reopen MainForm from within Program.cs? Sorry for the basic question but I'm learning.

Or close the first thread to be left with the second?

I already has a single instance class which sorted out multiple um, processes? But doesn't seem to work with in this instance.

Any help appreciated!

This is the contents of Program.cs

static class Program
    {
        /// <summary>
        /// The main entry point for the application.
        /// </summary>
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            _hookID = SetHook(_proc);

            if (Logger.LogFileExist() == false)
            {
                Logger.WriteLine("UserKey:" + Settings.Default.UserKey);
            }

            Settings.Default.PropertyChanged += new System.ComponentModel.PropertyChangedEventHandler(Default_PropertyChanged);

            if (SingleInstance.SingleApplication.Run() == false)
            {
                return;
            }
            Application.Run(new MainForm());
            UnhookWindowsHookEx(_hookID);
        }

        static void Default_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
        {
            if (e.PropertyName == "UserKey")
            {
                Logger.WriteLine("UserKey:" + Settings.Default.UserKey);
            }
        }
        /****************************************/

        private const int WH_KEYBOARD_LL = 13;  
        private const int WM_KEYDOWN = 0x0100;
        private const int VK_F1 = 0x70;
        private static LowLevelKeyboardProc _proc = HookCallback;
        private static IntPtr _hookID = IntPtr.Zero;

        private static IntPtr SetHook(LowLevelKeyboardProc proc)
        {

            using (Process curProcess = Process.GetCurrentProcess())

            using (ProcessModule curModule = curProcess.MainModule)
            {
                return SetWindowsHookEx(WH_KEYBOARD_LL, proc,
                    GetModuleHandle(curModule.ModuleName), 0);
            }
        }

        private delegate IntPtr LowLevelKeyboardProc(
            int nCode, IntPtr wParam, IntPtr lParam);

        private static IntPtr HookCallback(
            int nCode, IntPtr wParam, IntPtr lParam)
        {
            if (nCode >= 0)
            {
                Keys number = (Keys)Marshal.ReadInt32(lParam);
                if (number == Keys.PrintScreen)
                {
                    if ((wParam == (IntPtr)260 && Keys.Alt == Control.ModifierKeys && number == Keys.PrintScreen))
                    {
                        MainForm mF = new MainForm();
                        mF.CaptureScreen(500);
                    }
                }
            }
            return CallNextHookEx(IntPtr.Zero, nCode, wParam, lParam);
        }
        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern IntPtr SetWindowsHookEx(int idHook,
            LowLevelKeyboardProc lpfn, IntPtr hMod, uint dwThreadId);
        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        [return: MarshalAs(UnmanagedType.Bool)]
        private static extern bool UnhookWindowsHookEx(IntPtr hhk);
        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern IntPtr CallNextHookEx(IntPtr hhk, int nCode,
            IntPtr wParam, IntPtr lParam);
        [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern IntPtr GetModuleHandle(string lpModuleName);  
    }