Author: Jonas Bilinkevicius 

I am trying to get a list of the windows that will appear on the Taskbar (and 
perhaps on Alt-Tab). I have tried to find the ones with no parent windows, etc. but 
I cannot find the pattern.

Answer:

As far as I know it has never been explicitly documented which criteria Windows 
uses here. Try the following:
1   
2   function EnumWindowsProc(Wnd: HWND; LParam: LPARAM): BOOL; stdcall;
3   begin
4     Result := True;
5     if (IsWindowVisible(Wnd) or IsIconic(wnd)) and
6       ((GetWindowLong(Wnd, GWL_HWNDPARENT) = 0) or
7       (GetWindowLong(Wnd, GWL_HWNDPARENT) = GetDesktopWindow)) and
8       { skip WS_EX_TOOLWINDOW windows }
9     (GetWindowLong(Wnd, GWL_EXSTYLE) and WS_EX_TOOLWINDOW = 0) then
10    begin
11      { place code here }
12    end;
13  end;