Entrenchment game crashed during a multiplayer LAN game....

i have tried to play several multiplayer games with friends, i start off fine and get about 15-20 minutes into the game then it completely crashes my PC every time.

When i restart, a windows box pops up saying "windows has just recovered from an unexpected crash" i then click view details and it says "blue screen".

i have recently just reinstalled windows 7 64bit, literally yeterday. my computer should be more than capable of running the game.

Another point is that i used to use the impulse/Gamestop version of the game, and that ran a treat, never crashed, everything maxed and no lag, as soon as i use the Steam version of the game, it crashes in the first half hour of the game =/

Any help would be muchly appreciated,

thanks in advance

Apollo