Xperttool is more or less the company who made your cards version of afterburner
just be careful before you start messing around with overclocking.
read up on what you are doing before you do it.
you can find info on the net on how to overclock almost every card out there.
software like afterburner and riva tuner make it all too easy to do damage to your system with a few sliders.
the more you push the overclock the more heat the chip produces and the closer it gets to burning itself out.
I overclock my stuff as a matter of principle
manufacturers always back off the speed of the chips from what they are capable of to prolong the life of the components.
I on the other hand see a graphics card as semi disposable... if i get 2 or 3 years out of it that's good enough.
(after 2 years it will be hard for the card to keep up with the then current games and I'd be looking at a new one anyway) at the moment our GTX460's are considered mid range cards.
my CPU is also overclocked from 2.8 to 3.5Ghz (AMD phenom2 quad)