Since the dawn of smartphones, hard keys are becoming obsolete. Manufactures have gone from complete utilization of hard keys, to only having a few keys, such as the volume control, camera and power button. Are your hard keys gathering dust because your prone to using touch screen widgets or apps for these functions? What if you had a way to associate the hard keys to your advantage? With XDA member YukiXDA‘s WP7 hard key mapping hack, you can learn to do just that.
To achieve that you have to edit the dll keybdpdd_htc.dll you can find in your ROM (in IMGFS/OEM) section (there are equivalents for aother devices as HTC).
The OP suggests that the hack should work for all HTC devices running Windows Phone 7, and can possibly be adapted for other manufacturers like Samsung and LG. If you want to learn more, visit the original post for detailed instructions.