If you have read the Motherboard pages on this site, you will know that the settings for the processor front side bus frequency (FSB), clock-multiplier, and voltages, can be set by setting jumpers or DIP Switches that are on the motherboard itself, or by using the BIOS setup program. The BIOS is now the most commonly used method.
The user manual that comes with a brand-name PC or motherboard should have a BIOS section that provides information on the settings that are available. If you don't have such a manual, you should be able to download a copy in the PDF format from the PC or motherboard manufacturer's site for a particular make/model of PC/motherboard.
For your information, the BIOS can also be used to monitor the system, such as monitoring the processor's temperature, fan speed, and its voltages.
Consult a motherboard's user manual for information on its BIOS settings, or use Google for information. For example, you can make use of the Google search box provided at the top of this page (with its Web radio button enabled) to look for information on, say, the Execute Disable Function setting: bios + "execute disable function".
Note that the BIOS settings are not standardised for all motherboards. It is up to the motherboard manufacturers which settings they choose to make available for a particular model of motherboard. For example, if a motherboard manufacturer wants to restrict the ability to overclock the processor and memory, the BIOS settings that allow the overclocking of those components will not be made available. This is a good idea from a support point of view, because people with no knowledge about overclocking often jump in at the deep end and ruin components, which are then sent back to vendors as being dead on arrival.
