DVD Region Killer is a Software, that enables you to play DVD titles made for different regions on your PC, without the hassle to switch the region of your Windows operating system and / or the region of your DVD player software back and forth.
As you probably know, a DVD is usually mastered to play in a specific region of the world. The world is divided into 6 regions, for example USA is region 1, and Europe is region 2. A DVD mastered to play in the US (region 1) will not be played on a DVD player set to region 2 (Europe).
There are many reasons why the DVD Industry has set up this region restriction, but there are various reasons to overcome this restriction, too. For example, a lot of people are offended by "forced subtitles", when they prefer to watch a movie in their original language, just to name one.