This is done in your systems BIOS.
It should be in the area where your processor's frequency is located under core voltage.
I want to warn you, going too high with this setting could fry your processor!
Try it one setting at a time, do not try the highest setting first!
Try the next Vcore voltage up from where you are now at default, and test stability, if there is no lock-ups, try the next vcore voltage setting up from that.
You can monitor your temperatures with one of the following programs listed below
(no installation required)
Good luck and be safe, a processor is a terrible thing to waste.