   My openGL code or graphics card problem
  Apologies before hand for not showing code but this is a general question.I've got a PC with 2 gforce 5500 cards in it, next to each other.  When I run my opnGL demo it runs fine for a while, then polygons start to vanish, then it will lockup for a few seconds, then start and lock up over and over again. What I've noticed is if I start the demo off from first booting my pc it will run for about 15 mins without problems, if I have been working on my PC for a while it will only run for 3-4 mins before problems start.I touched the heat sink on each card, the second one gets very hot, the main one is almost to burn you hot.Does this problem sound like a card overheat problem, or is it more likely my code?  I should add because of the shape of the PC the cards are on top of each other with the heat sinks facing downover.can anyone advise. Thanks.   
  try running other 3d applications like games or demos.if they cause the same behaviour it's definitely the card overheating, if not, it's definitely your opengl code.   