most of the time (in my experience) i have discovered that its not the lack of cooling or overclocking that heats up the system, its the cd/dvd roms, hard drives, lack of space in the case that makes it hot as hell, i suggest you get an Alpha cooler for your computer or at least rig up a ventilation system to run air through/across the inside of the system.

Lo Hawkboy,
 
Are you using a desktop or tower case?
 
I had this prob on an old desktop case (it was 2nd hand from work).
I bought a globalwin case which sorted out all the probs. You can get them from here> http://www.overclockers.co.uk

I have a tower.

Got an exhaust fan? I make sure that the power supply fan is reversed and blowing out of the case. I also have a fan that sits in a card slot below my GeForce GTS Pro and blows air out of the case as well. Just because you are getting air in, doesn't mean it's getting out very well.

I have one fan on the processor, one in the power supply (blowing out warm air) and one in front blowing in. ;(

sometimes you have to take drastic measures..usually the intake fan (located in the front) doesn't have enough of an air vent to pull in air. I had to cut out a hole in the front of the case. Big temperature differece.
 
System Temp:
Without cut = 35C
With cut = 27C
http://member.giga.net.tw/stevenlin/athlon.html
 
(yah, i know, it's a crappy case, hehe)

I think an air conditioning system for a 550MHZ pc is a little over the top! Check to see if there's anything blocking the airflow (large bunches of wires positioned in the wrong place are very good at doing this!) also clean your system if it's dirty - dust is very good at insulating components. Finally get a larger heatsink/fan - the global win VOS32 is a very efficient system and is quite cheap. One final thing - make sure the core voltage for you're cpu is on the correct setting - I think it should be 1.7V for an Athlon of your type - although don't quote me on that!