Recent CPUs and even CPUs in the Pentium 4 era all have relatively high temp capacities. Average temps for a desktop can vary greatly depending on how you build or how teh comanpy has built your PC. Running a Zalman passive cooling system can be more effective than a stock windows CPU fan and adding a Zalmann active fan cooling unit can drop temperatures over 20C under load over a typical Intel cooler that ships with the CPU. That being said i7s have a relatively similar average temp as the C2duos and if yours is at stock voltages and timings then your going to be funning around 37-40C under normal use depending on ambient room temperature. Dont bee too worried by temperatures under extreme load. These CPUs are built to withstand temps upwards of 70-80+ Celsius without experiencing problems. If you seem to be running that high it would be a wise idea to check the thermal grease and or Fan seatings though. If you are running under normal load at anything higher than 50-55C you might want to get checked out for problems as well.
If you're having trouble with high temperatures, you should adjust some of the fans. My 8800GTs used to run at 70C and all I had to do was flip my side intake into a side exhaust and the temperature dropped from 75C idle / 91C load to 69C idle /84 load (now I can overclock much more).
Just feel around in your computer to see if there are any pockets of air that aren't moving or are excessively warm. You might need an exhaust fan near there. Intake fans aren't that important.