I run the 1.2 GHZ, Athlon and was having immense problems with it when it was running around 120 degrees, I've got a monster fan on that bad boy now and it stays right around 95 degrees with 2 case fans also to help keep the air clean in the box. You may also want to look at your Harddrive setup, I run IDE Raid and noticed that was causing quite a bit of heat too with the two IBM drives in there.
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