In order to start overclocking, first we must know the name of your motherboard. And we need some detail on the hardware you are using. Once we know that, the basic steps are:
1. Make sure you have superb cooling for your processor. With a stock heatsink(the one that came with your processor) you will get a slight overclock but with something like the Vantec Aeroflow.
2. You must getinto your BIOS, this can be easily done while your computer is booting up. The "Del" key or "F2" key should get you into your BIOS. once in the BIOS, you have to get to you clock speed settings and multiplier settings. At first, you should decrease the multiplier field and increase the clock speed (FSB frequency). On your processor, I have one too, the defualt speed should be close to or at 1.67Ghz, your default FSB is 133MHz(x2) to get the 266MHz multiplied once more by 6.25 to get 1.67GHz.
3. When you get to the highest achievable setting and the computer is stable, this requires you to do things in steps, You can then increase the multiplier. Remember that you are rebooting after saving the settings and you must do one setting at a time. Try not to skip levels. Once you get to the highest attainable yet stable setting, you can then add more voltage to the CPU. DO NOT ADD TOO MUCH VOLTAGE or you can kill the CPU, Increasing the voltage creates an exponential amount of heat.
The highest I got with me 2000+XP was 1.825Ghz which is a decent OC but I was using the stock heatsink.
Remember to work in steps and when your computer will not boot or video gets weird, reset the CMOS with the onboard jumper.
Another thing to consider is good quality RAM. Samsung, Crucial, Corsair, Kingston, and some Geil RAM will do the task. Also, try to use RAM that is rated at a higher speed, For instance use PC2700. It gives you some head room.
Intel Pentium 4 2.6C @ 3.51GHz Gigabyte GA-8IPE1000Pro 2004 GT Edition Windows XP Pro/SuSE 9.1 Pro ATI Radeon 7000 64MB 80GB Western Digital HDD 40GB Seagate HDD x 2 Lite-On DVD/CD-RW Combo Drive