You should work smart with lights. Use limited ranges for lights, dont fill ur entire laser-beam with loads of lights, dont use soft shadows unless the effect really visible ánd neccesary.
For the lasers themselves, using 2d planes with images of laser effects on them is much faster then using complicated bryce textures and lights or even volume textures and stuff like that. Even if you dont have photoshop you probably should be able to make something nice in something freeware like the Gimp or something similar. All this will speed up your renders and most likely make things less heavy on ur system, which might well avoid crashes.

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