This is a question from
:
Right now my favourite software for overclocking graphics cards is
MSI Afterburner. It's awesome. Very intuitive to use. You can follow my guide here on how to overclock a modern graphics card. It's different from the one you're looking at, but the same rules will still apply.
NVIDIA GeForce GTX Series Fermi Video Card Overclocking Guide (NCIX Tech Tips #78) - YouTube
I recommend googling/reading around a little bit to see what other folks are achieving with your card to give you some idea where to start.
I've also taken the liberty of discounting a single unit of that card just for you. You can buy it here:
NCIX US - Buy N580GTX Lightning Xtreme Edition - MSI GeForce GTX 580 Lightning Xtreme Edition 832MHZ 3GB 4200MHZ GDDR5 PCI-E 2XDVI HDMI DP Video Card - MSI/MicroStar - Great price and fast delivery