|If you don't have the manual for your board, get it here:|
Starting on page 4-10, study the BIOS settings. Here's my recommendations:
AI Tuning = manual
DRAM frequency = DDR2-533 (DDR2-400 would be even better)
CPU freq = 300
PCI express freq = 100
PCI freq = 33.33
Modify ratio support = enabled
Ratio = 10
C1E support = disabled
Hyper Threading = disabled
SpeedStep = disabled
If you run across any Spread Spectrum options, disable them.
If the above settings work, the CPU will run at 3.0GHz at 1200MHz FSB with the RAM at 400MHz (DDR2-800). If the system becomes unbootable, use the ClearCmos jumper to reset the BIOS, then start over.