I found some extra time today and recompiled the shader for shadermodel 2,3 and 4. Since your card only supports up to 4 I made sure to compile to the lower models too just in case. Keep in mind that the color and float values differ per models so the system's settings might look different depending on the model you are using. You can download the support package HERE. Simply import this package and it will auto-unpack itself to the proper folder structure. You can find the default material in the sourcefolder and change it's shader, or create your own material and override it in the inspector of the system. The proper way to spawn a system is shown below through the light menu and then clicking on LightShafts_2. The shaders themselves are now listed under a subcategory LightShafts-> Legacy. I tested it in the same unity build as you and on my machine it ran out of the box with every shadermodel. So you will have to tell me whether the new shaders work or not, as I do not own an older card to test the shaders on. This support package works both in the commercial and non-commercial build of the package. I hope everything works out. Cheers.