According to MSI Afterburner my CPU is 100*C and that can't be true. I think it's weird that bios says my CPU is 50*C When I start the computer and it also says my Motherboard I 21*C. I think its some form of sensor in the CPU that measures the temperature is broken. I have changed Thermal paste and I also cleaned the CPU cooler. Another reason why I think the sensor is broken is that I can run WoW on High without any lag and with 80 FPS. These are my specs:
It can very well be true. Depends on certain factors. If your cpu cooler is mounted badly, the cpu will get extremely hot in just a few seconds it takes to get to bios. If the cooler is so packed with dirt and debris that it's basically insulating the heatsink, same thing. And it doesn't matter if the cooler is stock, aftermarket air or liquid cooled, its all the same principle.
I still think it's weird since I have been gaming for one week without anything happening to my computer nor it lagging with it showing 100*C while gaming. Anyway, what should I start to replace, the cooler or the cpu?
Nothing. First pull the side of the pc and make sure the cpu fan is actually spinning. Check all connectors that they are landed right and not loose or hanging. Check the cpu cooler is tight or at least snapped all the way in. Verify everything visually and physically.