AFAIK yes, but you should check Intel's website for info on the 8400's operating temp. A CPU running that hot may also affect your PC's cooling ability, by adding more heat that your cooling systems need to deal with.
Your temps are a bit high. The system temp at 59 degrees C while idle is quite high. Are you using proper cooling in your case? I am assuming your CPU temp of 81 degrees C is under load which is quite high as well most likely because of the ambient temperature of the air in the case. Make sure you are using proper cooling.