cpu voltage in bios has 4 options..normal/+0.4v and another 2 increases i can't remember offhand. if i increase the voltage will i get a performance boost, i.e is it the same as over clocking and will it harm my cpu.
Increasing the voltage alone will give you no gains. The point of increasing the voltage to the CPU or RAM is to enhance stability when overclocking. Overclockers seldom use off the peg stuff, and specialist parts are used to dissipate the often dramatic increase in heat when pushing the voltage up. It's a great way to unleash the full potential of a system, but it'll likely kill a plain vanilla machine pretty quickly.