This function used to get start menu directory.

uses shlobj;

function GetStartMenu: String;
var
dir: PItemIDList;
startmenu : array[0..MAX_PATH] of Char;
begin
SHGetSpecialFolderLocation(Application.handle, CSIDL_STARTMENU, dir);
SHGetPathFromIDList(dir, startmenu);
result := strpas(startmenu);
end;

procedure TForm1.BitBtn1Click(Sender: TObject);
begin
Edit1.Text := GetStartMenu;
end;

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