I've only gotten this to work with XP, and i've tried but can't get it to work in win7 x64. (the registry is in a different place but even after figuring that out i had trouble)

Basically, this allows you to play Dark Crusade with all the starter races (orks, space marines, chaos, eldar, and imperial guard) without having the original game or winter assault installed (thus saving tons of hard drive space)
Also incredibly useful for LAN parties.