|OEM computers such as DELL do not stand up well to the extra stresses of overclocking. As a result, manufacturers do not include the settings necessary for overclocking in the BIOS. This protects you from failures and them from the resulting warranty claims. While it is often possible to overclock such systems the results are rarely satisfactory and the risks are high.|
Overclocking is best restricted to home built systems where you can control the specifications and quality of the components used.