Cant comment yet, so here is something ive found:
Setting a Windows form to be bottommost
so you only have to add this to your class / Form
[System.Runtime.InteropServices;DllImport("user32.dll")]
static extern bool SetWindowPos(IntPtr hWnd, IntPtr hWndInsertAfter, int X, int Y, int cx, int cy, uint uFlags);
static readonly IntPtr HWND_BOTTOM = new IntPtr(1);
const UInt32 SWP_NOSIZE = 0x0001;
const UInt32 SWP_NOMOVE = 0x0002;
const UInt32 SWP_NOACTIVATE = 0x0010;
and then on the Form.Activate and the Form.Load event you have to run the declared method like this:
SetWindowPos(Handle, HWND_BOTTOM, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE | SWP_NOACTIVATE);
Code from Richard Ev