Performance Drop after 10mins playing games

[Xellos]

Recently installed a new motherboard and hard drive after the old motherboard died

Did a clean install of Windows XP and all drivers, but for the last few days my framerate in games is dropping by 70-80%

Do you think my graphics card is on its way out?

Specs in sig

 

[Xellos]

Temps while playing games

Motherboard - 43 °C
CPU - 31 °C
GPU - 54 °C
GPU Memory - 56 °C
Seagate ST3160021A - 49 °C
Seagate ST3320620AS - 48 °C

 

[Xellos]

I think my PSU is a Thermaltake 480W+ (cant remember the exact number), but ive turned the fan right up and it hasnt slowed down as of yet.

Oh and the GPU is now hitting 87 °C

 

[Xellos]

GPU fan speed is always on 100%, have 4 case fans too =/