How to increase my i7-920 processor up to default speed?
I assume you're trying to say how to increase the speed of your 920 processor from the default 2.66 GHz, for faster calculations of your problems.
Then you've to do something called as "overclocking", which means to increase the clock speed of your processor, like for eg: instead of 2.66 GHz, you could run it at 3.0 GHz or 3.4 GHz or even higher.
This overclocking also requires you to tune other componenets of your system like RAM. But first, to offer suggestions, you'll need to give out the details of your entire system like motherboard brand, RAM speed, etc. Also do post it in the section for "Overclocking".