Assuming that you're talking about normal 2.1 powered speakers for use with computers, the main issue is you'd only have stereo inputs. The easiest thing to do would be to disable the subwoofer channel on your PC, giving you 5.0 output which should route the sub channel to the front left/right. Then run the front 2 channels to one system, and the rear 2 channels to the other. You'd need some other powered system for the center channel, OR you could disable center and live with 4.0.