The 1200 point download is Black Label DLC for the Mushihime-sama Futari ver1.5 disc release. Black Label was a different arcade release of Mushihime-sama Futari. It is essentially a remix of Futari. Personally I find it much more fun that version 1.5 and it is my preferred mode. Most people say that Black Label is easier as well, which is a bonus really.
It sounds like you just bought DLC for a game you don't own. Luckily for you the game is pretty cheap at the moment as its gotten a Platinum release. The game was only released in Japan but happily is region-free!
http://www.play-asia.com/Mushihimesa...n-70-3yu5.html