The problem with the cooling theory is that the graphic card works fine after reinstalling Windows. If it was overheating or broken, a reinstall won't help it. And a temperature below 90C is not critical for a graphic card.
Something else is bottlenecking the system. Most likely software.
Nono, the temperature isnt critical, but the activity is critical, when my card works good, the activity lies on 0%, now when i start WoW, it usually goes up to 50% pluss, and then everything starts to lagg.
It should always be close to 100% load on the GPU during gaming, if it's not being limited by something.
If it can produce 30fps with 50% load, it will just produce 60fps on 100% load instead of staying at 30fps.