With a better CPU cooler. What temps are you seeing?
Post your motherboard model and your computer case model, and your CPU model.
I purchased a Cooler Master Hyper 212 Evo for about $31 and it lowered my CPU temp at full load (Using Boinc Client) by 20c on the CPU.
Everyone's case and situation is different, so you might not get the same results as I did in my case, but you would improve.