I bought an amd althon 3400 Cpu and its not cooling the way i want it. its probably the cheap retail heatsink.

I have the Antec Super LanBoy Case which is a good case with good airflow. It has 2 120mm fans. The front one blows in the case while the back one blows out.

I want to add another 120mm fan to the side of the case so air will both on the heatsink. How can I do that? Below are some case pictures.

The easiest way to get a side blow hole is to get a bi-metal hole saw. They cut a nice round hole and are fairly easy to use. I have a 3" holesaw that I use for 80mm fans, it's just about the right size. A 120mm fan would need something like a 4.5"(not sure, measure your 120mm fan's blade diameter). A holesaw should cost about $20-30 dollars at Lowes/Home depot/etc. Then you drill holes for the fan mounts(4holes) of the right size.

I think you can get Third part windows with 80mm or 120mm ports in them, but it will be harder to find them then finding the saw. What is would do is find the computer mod shop in your city if there is one most cities do have them here in Canada, but then again the avrage home in Canada has something like 3.2 working computers per household of 4 residents at 31 million people you do the math on the amount of working computers, but some large citys in the U.S. don't, so if you can find one swing passed it if they dont have them go get the saw, I have a set of the saws as I am often doing computer mods, the saws are allso fun for building dowle and peg in hole things stands tables, chairs and the list goes on so the saws are not a waist of money.

it's a beautiful case with plenty of airflow. DO NOT mess with the case. get a better cpu cooler, should cost you around $20 (USD).
your cpu shouldn't be running with problematic heat levels anyways. adding a side fan would do little to help.

PS > i see you're from chicago too. cubs or sox?

Well if you know where to place the fan then it will be fine but the home work should be done. But yah you can buy real neat CPU Heatsinks and fans I like the copper ones that have a good even distrabution around the fan base.