glutGameModeString

why does glutGamemodeString have no effect?
Help!

int main(int argc, char* argv[])
{
HRESULT hr;
glutInit(&argc,argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);

glutGameModeString("640x480:16@75");        //GLUT 3.7
               glutEnterGameMode();                                         //GLUT 3.7
hr = CaptureKeyboard();     //TODO: hr check
hr = CaptureMouse();        //TODO: hr check

init();
glutDisplayFunc(display);

glutKeyboardFunc(keyboard);
glutIdleFunc(engine);
glutSetCursor(101);  //cursor none
glutMainLoop();
glutLeaveGameMode();

return 0;

}