Computer won't boot with 2000+ Athlon, 2100+ Athlon works just fine

I have a really strange problem going on. I have two chips, an AMD
2000+ and an AMD 2100+. They both work (they'll both boot the system
just fine). However, after the whole detecting RAM/IDE drives stage,
the 2100+ goes on to successfully boot into Windows while the 2000+ just
hangs at a black screen with a blinking cursor in the upper left.

This computer originally had the 2000+ processor in it and it worked
just fine. Then, I upgraded it to the 2100+ processor temporarily and
it detected the increase in processor speed and worked fine. Now, when
I'm trying to go back down to the 2000+, it's not working. Could this
be a driver compatibility issue with Windows - i.e. the 2000+ driver
would allow higher-rated chips, but now that it's auto-detected the
2100+, it won't function with anything less? I.e. upwards compatible
but not downwards compatible?

If you could tell me some way to change the drivers on this system so
that it would boot correctly with the 2000+ CPU, that'd be great.
Thanks in advance for the help.

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