Complete the following achievements to unlock Microsoft Gamerscore points.

Achievement	How to unlock	Points
ALIEN KILLER III	Kill 750 enemies.	100
ALIEN KILLER II	Kill 500 enemies.	100
ALIEN KILLER IV	Kill 1000 enemies.	100
ALIEN KILLER IX	Kill 2250 enemies.	100
ALIEN KILLER I	Kill 250 enemies.	100
ALIEN KILLER VIII	Kill 2000 enemies.	100
ALIEN KILLER VII	Kill 1750 enemies.	100
ALIEN KILLER VI	Kill 1500 enemies.	100
ALIEN KILLER V	Kill 1250 enemies.	100
ALIEN KILLER X	Kill 2500 enemies.	100