not a lot that can be done with an Intel motherboard, especailly an old model like that 845 based one.
with a decent mobo and cooling your 1.7ghz could probably reach 2.2ghz.
I've had a few 1.8's that could do 2.4ghz with out any real problem.
with your system I wouldn't worry about overclocking it...just start saving for an A64 or C2D system....much fun to be had with those setups.