The mainboard should support FSB 133, you should be able to set that in the BIOS.
But, you may need to run in asynchronous mode depending on your RAM, if you have DDR200 RAM and run that at 133MHz(which would be 266MHz effectively), it might be a bit overclocked and you could end up having to buy new RAM. I don't know whether old mainboards have any security mechanisms to prevent that.
This old review I found in google talks about how the FSB is set in the BIOS(they don't explain, just mention it). Well, you may want to have a look at your BIOS setting and if you are in doubt, don't change anything, but just browsing the various settings cannot hurt, it's how I got familiar with it.