Processor temperature

[jas61]

I am running and AMD athlon 64 x 2 dual core 6400+ processor. I had changed a heat sink and fan and I can't seem to get the temperature where I want it. A temperature fluctuates between 50 to 65. If I'm not mistaken the temperature should never run over 65c and that the highest any higher than that and I could be causing damage to the CPU in my right? Anyhow I'm asking for some suggestions on how to bring the temperature down and keep it from fluctuating. If it helps any my mother board is an asus M3a 770 socket aM2+ motherboard. It used to get so hot that the plastic tabs that hold the heat sink would snap off. thought it could be the mother board so I sent it back they sent me new one that has been a lot better but not where it should be so as I stated before I changed the heat sink and fan and again it's not where it should be it's OK but it's borderline any help will be appreciated.

[ViPeR.Ja]

you sure you applied thermal paste? to the heatsink and cpu

[skier]

is it overclocked at all? are those temps at load, or at idle(it is possible if you arent paying much attention that a program could be locked up causing your CPU to be at full load without you knowing it!) check the process manager and see what %utilization you are getting those temps at