Motherboard Moniter has worked well for me on more than one system, it's a windows freebie and easy to find. Use it to check your CPU temp, as a low fan speed can allow temp to increase, the fan speed itself can't directly cause a reset.
While 2.5k sounds a bit slow, I think it's probably enough for a relatively idle cpu. Check and make sure the fan in the power supply is blowing, too (with your hand). Watch the temp and see.