I have an Athlon XP 2400+ which has never run under full load hotter than 45C and thats with a standard heatsink and fan.

When it did get to the 45C I stripped down my PC cleaned everything and put it all back together (cables tidier) and now my CPU never hits 40C and its OC'd

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Rig Specs: Custom Built:
ASUS M2N4-SLI
AMD Athlon 64 X2 Dual 4600+
512MB SLI NVIDIA GeForce 7950GT OC
2.00 GB Elixiur RAM
400GB Hitachi SATA II HDD
Western Digital 120GB IDE HDD
Samsung SyncMaster 932B Monitor
More to follow soon.....