About three years ago, before Jumper Less motherboards were invented, users such as myself would have to open their case, grab a torch and search for the correct jumpers to change the core voltages, bus speeds and multipliers etc. Now thanks to Jumper Less motherboard technology which we first saw produced by ABIT, users no longer have to use jumpers or dipswitches to adjust core voltages, bus speeds and multipliers etc on most motherboards. Just about all motherboard manufactures such as ABIT, ASUS and MSI now have no jumpers on their motherboards. It seems Gigabyte have been a bit slow to catch onto this type of technology, some of their recent boards don't use a jumper free design. Now, where was I? I'll get back on subject now... Voltages!
Voltage is one of the main options which will determine a successful or unsuccessful overclock attempt. The higher you overclock your processor the more voltage hungry the processor becomes. Here comes the tricky bit, the more voltage you supply the processor, will result in higher processor temperatures. Each processor ships at a default core voltage, let's take the Intel Pentium "Coppermine" for example. This FC-PGA 0.18 micron process processor ships with a core voltage of 1.65v. When you attempt to first overclock the processor at this default voltage with no success you are normally forced to increase the voltage up in .5v increments to allow for the extra power the processor needs to run at the faster clock speed. PPGA processors based on a 0.25 micron process ship with a default core voltage of 2.0v. Most motherboards let you adjust the core voltage anywhere from 1.30v to 2.50v in small jumps. Taking the Celeron for example with a default core voltage of 2.0v, doesn't give you much room to play with when you can only adjust the core voltage to a maximum of 2.50 on most motherboards. The reason for FC-PGA processors only needing 1.65v core voltage is due to the small 0.18 micron size of the core, the PPGA cores are bigger at 0.25 micron and thus require more power because their cores are bigger.
Changing the core voltage through the BIOS is simple, but if done wrong can be fatal. you'll normally find the voltage settings where the FSB and processor clock speed settings are located in the BIOS. Once you find the voltage setting area in the BIOS, change the voltage to the required amount. If you have a Pentium III "Coppermine" processor don't increase the core voltage over 1.95v to be safe. If you have a Celeron processor don't increase the core voltage over 2.30v to be safe. If you want to know the default voltage of your processor it will be printed on the "sticker" of the processor.
If you are using a slot1 to socket370 adapter card (aka riser card) you will need to change the jumpers to suit your certain processor on the card itself, unless you have set the motherboard to over right the adapter card which will allow you to change the settings through the BIOS as mentioned above.