Play around your mobo, explore where you can find a place to manually set fsb, ram freq. timings, vcore and all that stuff. The only important things you need to adjust on overclocking are as follows:
CPU FSB
VCore
CPU Multiplier
RAM Frequency
RAM Timing
RAM Voltage
Disbabling C1E on the dual cores might be a good thing too. Note that "RAM" will say DDR on the BIOS.
All the rest you can set it to automatic until you know what they really mean.
I set the FSB Termination Voltage, NB VCore, SB VCore, ICH Chipset Voltage, PCI Clock Synchronization Mode and PCI Express Frequency are all set to automatic. And Spread Spectrum Disabled. Not sure what all these things does hehe.
But heres a summary from someone's guide:
CPU Frequency, once chosen just use the + or - option on the numeric keypad to push the FSB up for down, the limit is shown top right of the bios screen and is 100 to 650fsb. Real limit for most boards dual channel is 540ish at this time.
DRAM frequency is where you choose what speed the ram will run at, on the P5B this is directly linked to the CPU Frequency, so as you push up the CPU fsb the Dram frequency pushes up with it...a nice touch from Asus.
I have decided to explain the DRAM ratio's further into the artice so now we move onto:
PCI Express frequency.90 to 150MHZ is selectable, selecting 120 or so can add a healthy boost to PCIE bandwidth if the cards you have can run this frequency. This option needs to be tested thoroughly to see how much the video cards can stand.110 is usually very safe, 120 is starting to push it a little.
PCI Clock...just set this to 33.33 and forget about it.
Spread Spectrum is best disabled for overclocking.
Memory Voltage 1.8 to 2.45V, only supply the dimms the voltage they need to get the overclock or speed stable. I recomend no more than 2.5V for DDR2 maximum and with this board hitting 2.45V max you should be safe. Remember to cool the ram with a fan if you can.
CPU Vcore Voltage Auto sets the voltage the CPU is hard coded to set, I always set this and view the voltage in the hardware monitor section of bios so I know my start point. Remember more volts = more heat, on air cooling with C2D try to stay at under 1.5V, 1.6V with water and phase change cooling.
FSB termination Voltage useful option when pushing the FSB frequency high on the CPU, adding a little voltage here can help stabalise things as you clock higher.
NB Vcore Remember the memory controller is on the NorthBridge, adding some voltage here can have a huge impact on how well the CPU and memory overclock. Just remember if you set the max 1.65V to keep the NB cooled by adding a fan over the heatsink.
SB Vcore useful for adding extra voltage to the PCIE bus when overclcoking video cards and trying to run them on an overclocked PCIE frequency, I would tend to use 1.7v as a max here.
ICH chipset voltage I have found no need to alter this during testing, some say it adds stability, I set auto.