AthlonXP 2000 on MSI KT4AV with (VIA KT400A) chipset Mainboard has Speed

Learned scholars,

My AthlonXP 2000 on MSI KT4AV with (VIA KT400A) chipset Mainboard has Speed
Complexity.

The displayed CPU speed on startup BIOS is 1.25gHz with FSB setting of
100mhz. Actual speed of Athlon XP2000 is 1.67ghz as provided by AMD.

Upon changing of FSB settings to 105mhz, speed rises to 1.275ghz. At 110mhz,
speed is 1.330ghz. When set to 133mhz,
BIOS displayed 'ATHlonXP 2000' but then system went into a lockup/hanged.

At 266mhz, system could not be booted. I have to manually flash the BIOS
RAM to set back to default setting.

At 110fsbmhz cpu=1330ghz, system is not that stable. BIOS settings
sometimes will jump back to default 100mhz. Currently system is stable
under 100mhz cpu=1.25ghz

Or maube i was conned by the pc dealer into getting a lower speed athlon?

pls advise. thanks.