I run distributed.net's RC5 client, so the CPU is at 100% constantly. I was running about 70 degrees C for a while. I dusted everything out, and nI ran at 66 degrees. I kept it like this for a while, and it woulf fluctuate between 66 and 68 degrees. I add a case fan to the back, and now its at 60. This is under an absolute full load. I didn't think just a case fan would be that big of a deal.