Try different software. I like HWMonitor: http://www.cpuid.com/softwares/hwmonitor.html
A CPU doesn't actually measure degrees C, it measures how many degrees away from its max temperature it is (TJmax or similar). Monitoring software typically has each CPU's TJmax built in, but sometimes it defaults to the wrong number. So let's say it thinks the TJmax is 60C instead of 80C, and the CPU knows its temperature is TJmax-60.0C, your software will report 0.0C. Another result is lower temperatures are less accurate than higher temperatures.
Source: Rumors I've heard over the years.
On the other hand, if this reading is in the BIOS, I've got nothing for you.