i put the frequency from 166 to 200 and the pc wont boot plz help

CPU:
Athlon xp 3000+
OS:
Windows XP sp1
Mobo:
Gigabyte GA-7N400E-L nforce 2
RAM:
512 mb

Use the "Reset CMOS" jumper or [ull the battery on the motherboard to reset the NIOS default values...