The BIOS (Basic Input/Output System) is a program held on a small chip on your motherboard. It provides the instructions for what your PC should do as soon as it turns on. Your BIOS is independent of your operating system, which means that it is not affected by which operating system you use, or which version of drivers you've installed, or what your settings are in Windows for example. The BIOS supersedes all of that, and your drivers and operating system will load well after the BIOS has loaded up. The BIOS basically controls a range of hardware-related features and is the "middle-man" between your CPU and all the attached devices in your system.
All of this means that if there is an incorrect setting in your BIOS - that is a setting which is not optimal or correct for your hardware configuration - then you will have problems regardless of what you change in Windows, or which driver version you install.
As your BIOS starts to load, the first thing it does is the Power-On Self Test (POST), a diagnostic program which checks your components and makes sure everything is present and working OK. POST is usually extremely fast - blink and you'll miss it. You will only really notice it if it stops when encountering an error. POST error messages can be a bit obscure, but usually give you a lead as to where to look in your BIOS settings. A quick general guide to what the POST error beeps mean is here, but a more accurate indication is found in your motherboard's manual.
If you have no POST errors you will see your PC's startup screen, which shows such information as your BIOS type (e.g. Award), the key to press to access your BIOS settings (e.g. DEL, ESC or F2), the type of processor and its speed, RAM amount and RAM test, drive information, and so on. Note if any of this information is clearly incorrect, it may be that your hardware is extremely new and hence not recognized correctly by the BIOS, you've overclocked your PC too far, or you have bad BIOS settings.
At this point, if you quickly press the indicated key (usually DEL) repeatedly you can access your BIOS settings. If your BIOS has a password then you'll have to enter it first to access your BIOS settings. If you've forgotten the password, then try the following site.
- BIOS Settings
Once in your BIOS, there are a range of settings and they will differ based on which motherboard chipset and what type of BIOS you have. I cannot possibly cover them all here, nor can I give you the best settings as this will depend on your individual hardware configuration. What I can do is point you to this excellent Definitive BIOS Optimization Guide. The guide covers what each setting actually does, and when used in conjunction with your motherboard's user manual arms you with the information you need to figure out the best settings for your individual hardware configuration.
I do want to make special mention of RAM related settings, as it is almost a form of overclocking if you choose RAM timings which are faster than your RAM supports by default (see the above BIOS Guide for an explanation of RAM timings). Usually, your RAM default timings are determined by SPD (Serial Presence Detection). You can change these timings to increase RAM performance, but this can often cause problems along the same lines as overclocking other components (see the Overclocking section). Just keep in mind that if you're having any problems it could be the RAM timings as much as anything else.
- BIOS Updates
The BIOS is actually written on an EPROM (Eraseable Programmable Read Only Memory) chip, which means that it can be updated with new information. Motherboard manufacturers often release new BIOS versions which can improve performance, stability and compatibility, add new features or modify existing features, and fix known bugs. These new BIOS versions are available for download on the manufacturer's website, and I've provided a link to the support sites of the most common motherboard manufacturers below:
Go to your manufacturer's site, download the latest BIOS for your exact motherboard model and follow the instructions on the site to "flash" (update) the chip on your motherboard with this new BIOS. A word of warning - flashing the BIOS can be tricky. If something goes wrong and your PC won't boot up then you may have to take your motherboard to a dealer to have the EPROM chip replaced, so when updating your BIOS follow the instructions to the letter. In particular, make sure your PC is not overclocked when flashing the BIOS.
If you're feeling game, there are enthusiast-modified BIOS out there which may provide added functionality and performance beyond manufacturer's specifications. One place to download such BIOS is BIOSMods, but remember that playing around with BIOS is a risky thing, so take care.
It's important to have the latest BIOS simply because it can help improve your PC's performance while at the same time ensuring that any known bugs with the hardware have been resolved.