uses 
  ShlObj, ActiveX; 

procedure FreePidl(pidl: PItemIDList); 
var 
  allocator: IMalloc; 
begin 
  if Succeeded(SHGetMalloc(allocator)) then 
  begin 
    allocator.Free(pidl); 
    {$IFDEF VER100} 
    allocator.Release; 
    {$ENDIF} 
  end; 
end; 

function GetStartMenu: string; 
var 
  pidl: PItemIDList; 
  buf: array[0..MAX_PATH] of Char; 
begin 
  if Succeeded(SHGetSpecialFolderLocation(Form1.Handle, CSIDL_STARTMENU, pidl)) then 
  SHGetPathFromIDList(pidl, buf); 
  Result := StrPas(buf); 
  FreePIDL(pidl); 
end; 

Zdroj: http://www.delphitricks.com/source-code/systeminfo/get_the_startmenus_directory.html