I still think it's probably a problem with the mobo's sensor circuitry, but I'm just guessing.
If this were an isolated case, I would agree with that. But it is not. As I noted, I have seen several cases where the +12V was reading dramatically and unrealistically low. At another forum where I am on the Tech Team, we (other techs) have a running thread on the discussion with at least a couple dozen examples where the computers are running perfectly fine, but +12V is seen as drastically low - all with Win7, BTW.
Sorry, but it is not true that voltages in BIOS are not under load. If the PSU is connected to the board, there's a load. And if the computer is running, even in the BIOS, the fans and drives are spinning, the CPU and RAM are "live" and running, as is the graphics solution, drive controllers, etc. There is a very real resistive
Temperatures, on the other hand, are different. Running the BIOS Setup Menu is about the least demanding task we can ask of our computers. And so temperatures in the BIOS are likely to be lower than when the computer is running Windows and doing "real" tasks.
I also agree to use the motherboard maker's monitoring program, but I note it too will run under the OS, and it will use the exact same sensor devices and any other monitoring program.
And if this is a Windows or W7 problem, it will not make a difference - as is the case with me. I note my PSU +12V measures +12.32V with my multimeter when connected to the motherboard and running Windows. The BIOS shows 12.2V, as does my FrozenCPU Ultimate PSU Tester
. However, all Windows based HW monitors are showing 5.6 to 7.1V.
So at this point, I think it is a Windows problem, and not a hardware issue as I note in a couple of those examples, voltages were good with XP or Vista, but not after upgrading to Windows 7.