I am not sure about version 5 as I have 4.16 but if you look under the "General" tab and then click on the "System" button it should list the three sensors. at this point you can click on the down arrows to the right of each of the sensors to select a different one as the 255c reading that you are getting is incorect. As I don't know what type of equipment you are running I will give you an estimate of about 32c for idle CPU temp and maybe 42c or so under load. The sensor that shows your case temp will be a few degrees high than your room temp. Once you figure out which sensors do what you can rename them under the "Visual" tab. Hope this helps and good luck.