ASUS P5N-D LGA 775 NVIDIA nForce 750i SLI ATX Intel Motherboard help

i just put together my computer, and i'm not the best with thme. i'm learning though. i've been trying to findout what the NB threshold is. currently mine runs at about 42 to 44 and whenever i start doing anything it jumps to about 45 - 48. 48 being the highest i've seen it at. the alarm for my PC probe goes off at 45c and that gets annoying seeing as it likes to jump back and forth between 44 and 45c. i believe this is the stock setting for the prode, not sure. so can anyone tell me where i should set at what degree the probe should alarm me?

if i left out anything tell me and i'll do my best to add it.
thanks