Taken from the original Forum post by Bilge:
DC Race Unlocker does what it says on the tin. Plus a little more. The main benefit of using this application is that it avoids tedious and sometimes confusing steps involved in editing the registry to enable your other races, without having to install the other games.
This application also avoids having to copy any files from any CDs. Simply enter your CD keys and all your races will be unlocked.
Further, if your DC installation is not detected due to missing registry entries, the application may "fix" your registry if you show it where your DC executable is located. This may be most useful if you format your Windows partition but still have the game files on your hard disk, in which case the application will recover your registry to the correct state.
You may also use the application to change any CD keys at any time. This feature may be useful if you mistype your CD key at install time, or share keys with your family but later decide to purchase additional copies so that you may both play online simultaneously.