KenAF Those vcore options are for the williamette I believe. These options came with the 1003 bios version.
BIOS Setup allows adjusting the processor Vcore. For CPUs built on Willamette the Vcore can vary from 1.75V to 1.85V with an increment of 0.025V, for those on Northwood from 1.5V to 1.7V with the same increment. For extreme overclockers ASUS P4B266 offers a special jumper, which allows increasing the top limit for Vcore up to 2.1V for Pentium 4 (Willamette) CPUs and up to 1.75V for Pentium 4 (Northwood) CPUs.