Build.prop Editor is an application that, once installed, lets you modify build.prop files. To use it, you'll need a rooted device. It's also very important to make sure you know which files to edit and how, since modifying build.prop files in any way can cause problems on your device.
Build.prop Editor is a simple and lightweight application that takes up less than 100 kilobytes. If you have a rooted device, this is a great way to get your hands on some new tools.