Motherboard Monitor' ">http://mbm.livewiredev.com/ works great for me. Speedfan works equally as well, though I have a fan controller, which makes it almost pointless for me to use it.
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AMD Opteron 165 CCBBE (2.7GHz @ 1.35v)
DFI CFX3200-DR (07/28)
Kingston HyperX DDR500 (3-3-3-8-1T)
Asus Dark Knight Radeon 4870 1GB
Audigy 2
2x 74GB Western Digital Raptors in RAID0
500GB SATA-300 WD Drive
CoolerMaster RealPowerPro 850W
NZXT Zero full-tower case
Windows XP Pro SP2