|How about listing your system specs? There are dozens of CPUs that run a 2.1GHz.|
"I'm quite afraid because my cpu sometimes gets to 65C.."
What's there to be afraid of? 65C is on the warm side but its certainly not in the "danger zone". Besides, it's impossible to overheat a CPU to death because they all have thermal protection circuitry. The CPU will automatically shutdown long before it'll overheat/burn out. And once it cools off, it will work fine again. If you feel the temps are too high, the problem is most likely with the heatsink/fan installation, not how many case fans you have (or don't have).
Who installed the heatsink on the CPU? How long ago? Is it a factory heatsink or aftermarket? What type of thermal material was used between the CPU & heatsink? Are you sure it was applied properly? When's the last time the heatsink was cleaned of any dust build-up?