the answer is more times than not NO. We hardly ever use our processor to the full extent of it's capability for the sheer fact that it's limited by other devices. In games you're limited to your video card's GPU and RAMDAC, is windows you're limited to your RAM size/speed and hard disk speed. Even installing programs limits you to your cdrom speed. There are a few things though that use it... seti, rc5, anyone else name a few? Don't get me wrong, there is a difference between let's say a 500 mhz machine and 1000 mhz machine in windows performance, although not much. The cpu will pick up for other lagging parts, like video cards in games and such. But who cares, it's all about having the speed... duron 600 @ 1000!!