This really isn't an effective method, the results will fall far short of the effort required.
Dark basic primitives are not the most optimized of models and complex objects made from them will have a lot of unneeded geometry, slowing performance, and such objects would be extremely difficult to texture with any detail.
I would recommend that you continue searching for a modeling program which you are able to use. There are so many out there across the range from high end to introductory that one of them is bound to run even on an older computer.
Good luck and stick with it! it's worth it.