|You need to include exactly what memory you are running (speed).|
You need to include what graphics you are running (onboard or what card).
It would be useful if you include detailed info on your power supply including make, model, wattage, and listed amperages.
It is important to know what use you plan on for this machine and what you expect out of it (gaming, office use, just web & email, etc. and how much improvement you are expecting).
You need to be reasonable in your expectations. If you are expecting to play modern games, multitask, run Windows 7, or run like a modern PC, you will be disappointed. Yes you should be able to overclock it, but even if you found a decent buy on a Pentium 4 3.2GHz 800MHz socket 478 processor and used that and have DDR400 memory (max for the board), and overclocked it, you still need to understand that the additional performance you will get will still be modest by today's standards.
If you plan on running older legacy games, even arcade type games, you will need to get a decent AGP graphics card if you do not have one. This will improve graphics performance, free up system memory, and off load graphics from your CPU (your onboard graphics assumes that the CPU will take on some of the work load).
Supply this information and if you do not expect too much and do not plan on wasting too much money on an outdated system, then we can help you overclock it. If you plan on loading all kinds of new components and expect significant improvements or gaming performance, then do not waste your time and money and save up for a new build from scratch. Even a modest build of a couple of generations back Core 2 system would blow the doors off what you can achieve from your system and a more modern i-series system would make that look like it had training wheels on.
You have to be a little bit crazy to keep you from going insane.