Bad sensor?

Hello,
Have a computer that was shutting itself off, so took off cover and cleaned it out ( we very dusty in there) also ran all kinds of virus tests and cleaned it up real good. It was running great after that. I decided I should put a temperature program on, so I could see if it was over heating. To my shock it read the temperature of my hard drive was 214 degrees Celsius! anyway I checked the bios temp and it was ok at 32 - then i installed a different temperature program and it was also over 200 - suddenly the temp went to just 7 ! so obviously those programs are reading something odd. It has even read as high as 342- lol - I just don't know what that means - why are those readings going all over the place even tho my bios and the program everst read normal .. Should I worry?