Your FSB is running at 100MHz instead of 133MHz.
Just set your FSB to 133MHz in BIOS.
Since the Athlon MP 2000+ has a x12.5 multiplier, you get 1.25GHz(100x12.5) whereas with a 133MHz FSB, you will get 1.67GHz(133x12.5) which is the correct speed for an Athlon MP 2000+
More info here
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