dont switch image

hi, 
RealTech's free OpenGL Extensions Viewer says
my laptop support opengl3.1
my Desktop PC support opengl2.1
i tried both computer
in the laptop work fine.. but on my very old computer Desktop PC dont change the image.. stay still on the first image.. the tutorial (http://duriansoftware.com/joe/An-intro-to-modern-OpenGL.-Table-of-Contents.html) says opnegl 2.0 so should work
