temperature discrepancies b/t bios and programs

[blast0x]

I just built a system with:
Gigabyte DS3
E6300 w/ Freezer 7 Pro
2GB OCZ Platinum DDR2 @ 5-5-5-15
7600GT

At stock speeds, bios shows my cpu temp as 43. On idle, Core Temp tells me 51/50 (cpu1/cpu2), and SpeedFan says 46/45 .
Now I'm running it at 400MHz fsb (2.8Ghz), and bios shows 46. Core Temp says 58/57 idle and 66/65 on full load. Speedfan shows 50/46 at idle and 50/56 on load.
Why are al these numbers so different?

When I was mounting the HSF a tiny bit of thermal paste smudged on the processor before I finally positioned it correctly. Also, I did not wipe the top of the cpu or anything before mounting because it seemed pretty clean already. Could that make a big difference?

I'm thinking of mounting the stock HSF to see what temps I get with that. What is the best way to remove the thermal paste off of the cpu?

 

[wee96]

I sit around 37c at idle on my freezer 7 pro, and around 50-53c at full load both cores. I'd try re-seating first, your definitely going to get better temps with the freezer than stock when its on right.

 

[SeetheSeer]

Use 90%+ Isopropyl alcohol. It's freely available at most stores. Lint free cloths are supposed to work better, but I just use toilet paper. You can use coffee filters if you want, those are lint free and disposable.

 

[wee96]

Ive always used paper towels with great success.

 

[blast0x]

Thanks for the suggestions.
So which temperature reading should I trust?