You can also check out our own tech support section. If you want official support, head on over to Fox Interactive's official tech support page. Skirmish is just a SP version of Co-op. Neither one has a real goal. Basically you go in as anything but an alien, and you have to kill hoards of Aliens until they kill you, then you respawn and keep killing.
Aliens are the only species in the game that attack in large droves.
The Predators by their nature are loners, and Marines usually group themselves as squads. The Aliens do not follow this rule, and will for the most part attack on sight. There are six cut-scenes, although various movies show humans in the vid screens. These are Smacker files, and you will have to download the player for them if you want to view them. The cut-scenes are available at the beginning of episode one and the end of the last normal episode for each character.