I have a mobo based on the 845GL-chipset, and it runs perfectly with a 2.4 GHz Williamnette Celeron.
The same mobo (It's a Dell Dimension 2400) can run with 3.06 GHz HT P4:s aswell, so there shouldn't be any problem.
Keep in mind that you might have to change your memory if you change bus speed.
Of, course, there might be some BIOS-specific limitations, but that's not very likely.
