Is it possible that I could overclock my CPU better with win 98se than now with winxp pro?

Somtimes winxp just wont boot
for example 12 * 133 ---> 1600mhz works with win 98se, but it wont work with winxp.
How is this possible?

My specs.
T-bird 1400(266)
256 (266)
maxtor 30 gb
gf mx200 (32 mb)