What exactly did you change in the bios settings? In other words did you change voltages on just cpu or NB, SB (mcp and spp i think) and what memory? All settings please!
Didn't change NB or SB voltage, didn't increase CPU voltage. Had to increase VTT voltage to max 20% otherwise its not stable at all. disabled all features like spread spectrum, C1E and so on. Tried memory on different timings but left it on 4-4-4-4-12 as doesn't make a difference. Increased FSB to 1400 and memory to 700. I have tried upping all voltages in different combinations when trying to go over 1400 but its just not stable.
to get any higher than what you are at now you will be tweaking NB/SB voltage and rest of bios. You should be able to run memory higher than 700 if you have PC6400... what kind of memory do you have?