what is the best rendering program to use on solid works 2004?

It really depends on what you are rendering, the type of images you desire, and if the workflow of the program is intuitive to you.

There are dozens of rendering applications available which will accept SOLIDWORKS models in either their native format, or through a common file format like step, or stl file.

Keyshot is a popular rendering application, but if it is "the best" can't be said.

Thank you for your input it is greatly appreciated.