I have one too.
I've always read that the maximum would be 2.0Ghz (that's what I have).
But, I believe that it is possible to put one faster as long as is has the same FSB speed witch I believe is 400Mhz (in this case on 2.0Ghz is 5*400Mhz).
If you can find a 2.4Ghz (6*400Mhz) I think it would work on it because the multiplier is usualy locked and the motherboard will not be able to change the CPU top speed.
The only thing I think you should worry about is the temperature that this CPU may be able to produce, and if you get a low quality one you may get in trouble...
Best Regards, hope have been usefull with this info.