GPU not detected after dusting my PC

The PC was running fine until I decided to strip it down—removed the cooler to repaste the CPU and pulled the GPU (an HD4870) to blow out the dust and apply fresh thermal paste. Since then, the card has effectively ceased to exist; my frame rate has plummeted from a steady 60 down to a pathetic 5 or 10. Even though all the fans are spinning and the GPU temperature reads a reasonable 67.5°C, the card itself feels scorching to the touch.
I perform this maintenance every few months without issue, yet today was an anomaly.
Any advice on how to fix this? I have GTA and Battlefield waiting for me.

Angela Richardson said:The PC was running fine until I decided to strip it down—removed the cooler to repaste the CPU and pulled the GPU (an HD4870) to blow out the dust and apply fresh thermal paste. Since then, the card has effectively ceased to exist; my frame rate has plummeted from a steady 60 down to a pathetic 5 or 10. Even though all the fans are spinning and the GPU temperature reads a reasonable 67.5°C, the card itself feels scorching to the touch.
I perform this maintenance every few months without issue, yet today was an anomaly.
Any advice on how to fix this? I have GTA and Battlefield waiting for me.

Did you actually get the new thermal paste on the GPU core?
Something didn't seat right, for sure.

I applied new thermal paste to the GPU.
I honestly have no idea what’s wrong with this thing; I even took the card apart to redo everything, but nothing works. I'm running out of ideas.
Does it make any difference if I swap out those power adapter pins on the graphics card?

The issue is resolved; there was simply insufficient thermal paste applied to the processor.