Which temp is right?

I've overclocked my E4400 to 3.0GHz. I have an Abit F-190HD mobo (radeon xpress 1250 chipset).

Heatsink: Thermalright Ultra 120 Extreme
Thermalpaste: Arctic Silver 5
Fan: Aerocool 90 CFM 120 mm

I'm being given 3 different CPU temps by 3 different utilties.

The BIOS and the Abit EQ utility give me a CPU temp of between 4 to 1 C.
From SpeedFan 4.32 I'm getting: 1C for CPU, Temp1 is 6C, and Core 0/1 are 30 C.
From Core Temp 0.95 I'm getting 44 or 45 C for both cores.

SpeedFan 4.32 also says I'm getting 6.6 V on the 12V, but the Abit EQ says a more normal 11.97 V.

Obviously the 4 to 1 C readings for CPU temp are erroneous, as is the 6 C Temp1 reading (what is Temp1?) and the 6.6 V reading from SpeedFan.

Which one of the above readings is correct, however? 30 C or 45 C? Also, why am I getting these erroneous readings, even from the BIOS and Abit utility themselves?

An easy way to check which reading is the CPU in speedfan is to load it up, then run something like Prim95 to stress your CPU.

The temperature that rises steadily is your CPU temperature

The core temperatures are the temperature of the cores themselves (rather than the CPU as a whole) and typically will be quite a bit higher than the CPU temperature.