Advancing the speed of a componant past the stock factory speed. You can overclock things like CPUs, Video cards, and RAM (not sure on RAM though). It can be dangerous if you go for something too high, and not know what you are doing, but done right many good things can come of it. Heck I got a processer that dosnt exist thanks to overclocking (P4 3.4Ghz stock to 3.9Ghz) and I am soon going to O/C my X800 PRO to a XT speed and save about $50~60 dollars.

PM me for specific details on how to do it.

Let me just add:

Manufactures routinely "underclock" most hardware because they have no idea what kind of enviorment they wiil be installed in.

So, they often set default clock speeds lower than it can safely run at (with good coolling) to acomodate systems with less than adequate cooling, etc.

Having said that, when you overclock, you still do so at your own risk.

Remember, if you toast it it's your loss.
As said though cards are way underclocked and it's quite disgraceful. I found this out only the other day when looking at my card. I am going to post it soon asking for some settings if anyone else has overclocked it, just as a starting point.