Is there any free software out there for designing things like projectors?

I need something simple that'll allow me to put specific objects in (LCD, lens, mirror, distance etc.) in and play around with it in the computer till I find the optimum ideal configuration.

I've got my first basic 'shoebox' projector up and running but I'm realizing I want a vertical projector due to space constraints, building this one has proved to me that I can build one and make it work so I'd like to make something better asthetically.
I have an idea for a design, a fairly complex design that's just about big enough to accomodate a 15" screen with a single mirror, but working it out on paper won't be easy and using some design software would help considerably except I don't know what to look for.

Hi Haku,

I found a free cad software called A9Tech. It is free. Hope it help if not it might point you in the right direction.

Thank you for that, I've downloaded and installed it, now to get to grips with it and use that to make all the major mistakes before I start cutting up wood/metal

Hopefully I should be able to use the guts of the projector I built for this new design, which may incorporate a mini-PC as there appears to be enough space.

Raytrace should help you with the 2D side of things:

http://members.ozemail.com.au/~imesoft/