Why is my bios showing a different cpu temp?

[Gone Cruising]

This is my first build and I have re-seated my cpu cooler 3 times now. Core Temp & CPUID both read my core temps at 51 to 55 C idle. The bios reads 41 to 45 C idle. Why the difference and what is my actual temp? Any help for a noob will be appreciated!

There are 6 case fans running...running 1.3 V on auto.

Overclocked it to 3.6 and CPUID temps showed idle 62 to 65 C...got scared and reset bios to stock.

http://i163.photobucket.com/albums/t304/carpenterk2006/CPUID.jpg

System:
Case: THERMALTAKE ARMOR+ VH6000SWA
CPU: Q6700 @ 2.67 (stock)
CPU Cooler: Asus Arctic Square
GFX: EVGA 9600 GT SSC x 2 SLI
Ram: Crucial Ballistix Tracer 4GB DDR2 800 PC2 6400
MB: EVGA 780i A1 SLI
PSU: Thermaltake Toughpower W0155RU 1000W
OS: Dual Boot XP & Vista Ultimate
HD: 2 x 150gb Raptors Raid 0 running XP
2 x 250gb Hitachi Deskstar Raid 0 running Vista
750 GB WD7500AAKS 7200 storage
1TB Hitachi Deskstar 7200 backup

 

[Evilonigiri]

The temp in the bios is probably the Tcase, which is the thermal sensor located between the cores while Core temp is reading the temps at the core. Trust Core temp, not the bios.