OK heres the SIMPLE way, found out by accident, just did it yesterday.
When you pop in a Celeron II flipchip the bios only gives you as high as 1.7v User Define, just shut down PC, switch off or un plug power supply, pull jumper for CLEAR CMOS place on 1-2 for about 30 seconds then replace to 2-3, dont pull battery or you'll loose everything! Reboot go to setup and redo all your settings. in CPU setup you should have all the voltages available past 2.2v I think. I used a Celermine 566@893 mhz,1.8v 105 buss on ZM6. Good Luck!
The "BIOS trick" that you've heard floating around is probably the method where you set your cpu voltage to it's peak, in your case 1.7v, and reflash with the latest BIOS. By then you supposedly should be capable of 2.0 volts max.
Give it a try if you haven't already. I'd like to know how it goes.