Lighting Design Help... CAD that is free?

I am designing the lights for my school talent show in 2 weeks, i am looking for a CAD that i can see a preview of what the stage looks like with the beams of light and such. Also, if there are any ideas for cool effects? I am pretty limited to about 30 Source-4s and about 10 Fresnels. Oh and we have two cyber lights mounted in the back of the Theatre. I don't know the size of the stage or anything, and would like to get the design done this weekend so when the week rolls around i can get to hanging them. Thanks! i will give best answer!