Shaders

I have two basic questions about shaders.
1)Will they run on graphics devices that not have programable processors, ie. one TNT2? It is if my machine doesn´t have a card with vertex or pixel shaders, the shader program will be emulated by software?
2)Loops. How does it manage in cards that vertex & pixel shaders do not allow this capacity of loops. The answer that I imagine is that the shader will create all the possibilities of the program’s flow and keep them for use the correct real shader whith dependence of tha actual state, ie numberof lights.
Thanks