The first step to overclocking any component on your PC is to update the BIOS on your motherboard. BIOS, which stands for "basic input/output system," is like a proto-operating system that governs the vital functions of your computer--i.e. your keyboard, the monitor, CD drivers, hard drives, etc.--before your operating system (Windows, OS X or Linux) boots up. As such, everything that is attached to your motherboard can be controlled by the BIOS. The BIOS isn't stored on your hard drive like the rest of your files. Instead, it's held on a volatile memory storage on the motherboard itself. This is a battery-powered CMOS chip that keeps track of any changes you make to the BIOS. If you remove the battery or the battery dies, then the BIOS returns to the factory settings (keep this in mind in case you make a mistake!). To upgrade a BIOS, you have to overwrite the data on this memory chip with the latest version.
Upgrading your BIOS isn't necessary for overclocking, nor is it likely necessary if you dont' make any hardware changes to your configuration. But if you are installing a new fan, new CPU or a graphics card, a BIOS update may be needed in order to ensure that your motherboard knows how to handle the new technologies that have been developed since the motherboard was built. Also, most of the overclocking tweaks are done from within the BIOS, so it makes sense to have the latest version.
Before you begin, you should know that it is possible to corrupt your BIOS on your motherboard. If this happens, your machine will not be bootable. While some motherboards have backup CMOS chips, in most cases, a corrupted BIOS is unfixable. Proceed with caution.
The first step to flashing your BIOS is finding out who manufactured it. This is usually printed on the motherboard itself, or you can find it in your computer's documentation. You may also find this on the OEM's website, if it's from a major manufacturer such as Dell, ASUS or HP. But make sure you look up the details for your particular model and year.
You can also use a program called Sandra to determine your main board's information. Get it here: http://www.sisoftware.co.uk/
In a best case scenario, your manufacturer will have an updated BIOS for your motherboard and will have an automated installer. If this is the case, stop reading this tutorial and carefully follow the instructions from your motherboard's manufacturer.
If not, you'll have to flash your motherboard BIOS from DOS. To do this, you'll need to download the updated BIOS file from your manufacturer and create a DOS boot disk. You can download a DOS boot disk image from http://www.bootdisk.com/. Download the "Driver Free Disk for BIOS Flashing" and copy it to a floppy disk. Or, download the ISO and copy it to a CD or DVD.
On a separate disc or disk, copy the BIOS files you downloaded from the manufacturer's website. There will usually be at least two: the BIOS itself and an installer with an .exe extension or .bat extension. Reboot your system with your boot disk inserted. This will bring you to a DOS prompt. You can now remove your boot disk and insert the disk with the BIOS. Run the .exe. or .bat file that you copied earlier. When the installer asks for the location of the bios file, tell it A:\\ or D:\\ or whichever drive you have your disk or disc inserted into. Follow the onscreen instructions, and if given the option to save a backup of your existing BIOS, take it.
DO NOT REBOOT OR TURN OFF THE COMPUTER UNTIL PROMPTED TO DO SO. Wait for the installer to finish completely, otherwise you may permenantly corrupt your system. When the installer is finished, remove any media you've insert and reboot the system.