Well, because of heat issues, the P4 Prescott is generally a poor overclocker. But, in the event that you feel you can safely do it you would have to find the BIOS setting to change the processor speed. This varies form motherboard to motherboard so I can't tell you where to find it, but once you get it we can help with overclocking.
Indeed it is. Find the multipler value too. You found the FSP (Front Side Bus). Multply the FSB by the multiplier and you should get your frequency. For example my FSB is 200 with a multipler of 11. That gives me 2.2 GHz. If I want 2.5 GHz then I make the FSB 227 MHz. 227*11=2497 MHz or 2.497GHzVoltages are also overclockable and at some point you will have to mess with your memory clock and/or latencies but that is more advanced.
My multiplier is 15.0 so if i want 3.5 GHZ i should set the value to 230-245 right? What's the limit for this type of CPU?
Yes, 233 MHz FSB will give you nearly 3.5 GHz (3495 MHz). That is a bit high for a 3 GHz P4, however. I think you would hit some fairly severe temperature problems at that speed. I would recommend sometihng around 3.2-3.3 Ghz. Even that may be too high.
