If you disbale those you will see solid CPU speed and voltages, and yes the temp will be more stable and possibly warmer too. And no, they shouldn't jump from 25 to 40 in one second, that is way to fast so it's probably the software reading something incorrectly.
I am using both core temp and the core temp windows gadget from the page you linked. They both bounce by 10-12 degrees C literally each second. In the bios main screen, the 'CPU Temperature" fluxes between 32c and 34c but no further.
I do have another odd thing occurring. The PC will be powered off, Windows, Shutdown, Off. And at least once a day it will power itself on. It's happened 3x so far since the build on saturday. The first time I thought I had forgotten to shut down. So last night I shutdown and waited to make sure everything was off. When I got up this morning it was powered on again. According to the system log, it powered up at 5:30am this morning on it's own. No programs were running and no error messages were present, it just started up. There were no tasks scheduled in Windows, and i would like to think powered off it wouldn't matter. I checked the 'Power Management Setup' in the Bios and it is set as follows:
ACPI Suspend: S3
Soft Off: Instant Off
PME Wakeup event: Enabled
Power of Ring: Disabled (no modem installed anyway)
Resume by Alarm: Disabled
HPet: Enabled
HPet mode: 64bit
Power on by mouse: disabled
Power on by Keyboard: disabled
AC Back Function: Softoff
Erp Support: Diabled
The only PCI card in the PC is the graphic card. Have you ever seen anything like this? It doesn't hurt anything, but my PC powering itself on is a little too HAL 9000 for me. In my half awake state this morning when I saw the orange glow coming from the case I customized, as I murmured 'Why wont you stay off?' to no one in particular, I half expected to here, "I'm sorry Duncan. I can't do that" come from the PC as a reply.