I think you'd get more useful results if you can manage some more substantial upgrades. Post a budget. Even a low-end AMD system will blow a P4 away.
+1 to mi1ez. Money spent on a higher-clocked P4 is money sent right down the crapper.
Do you have PCIE or AGP on that system? If PCIE, going to a 4670 GPU is a six-tier jump on Cleeve's chart, would run on that PSU, and would only set you back about $80.