Have Dell P4 1.7Ghz – Want to Upgrade Processor

I have had my Dell P4 1.7Ghz computer for about 10 years now. I want to build a new computer but don’t have the money to do that right now. Until I can get the money together, I was wondering if I can upgrade my current setup with a new processor. I’m just not sure which processor I can use and not sure what kind of performance boost I can expect. Any and all help is very appreciated.