I have a AMD 64 3500+ with a zalman HSF, not sure what model and arctic silver 5 thermal paste. Before I got the arctic thermal paste my system would idle at about 60 Celsius. Now I have the arctic silver 5 thermal paste it idles around 43 Celcius and 59 celsius under full load. I have heard that 28 or 30 celsius is ideal. How can I make the temp go down? Is it something to be worried about at 40 celsius? I have gotten the temp down by 20 celsius.

thermal paste just heps fill in the air gaps between the CPU and heatsink allowing more heat to come through to be cooled off
changing brands/types of paste at this point will have a minimal effect

well thers a few way to approach this

1)bigger fan and heatsink
seems prety self explanatory i would recpment reading up on some overcloaking forums
such as

2)rethink / optimize the airflow inside your machine
look at how the air flows through your machine and try to set up a nce flow throughout the computer
this may requier some modifications to the case depending on how you want to get into it
there was an article on this somewhere recently that i can't seem to find
but this ones got the basic ideas behind it

3)move to liquid cooling system
moving to a liquid system can cut down on noise and reduce heat but it requeres a whole new set of components as well as space for them