Opening part file opens/loads assembly

I'm running SW 2009. Starting with no files open, I open a.sldprt file that is part of an assembly. Opening this .sldprt fileopens not only the part file but the assembly and a couple of other.sldprt files within the assembly. Since the assembly is somewhatlarge, it's wasting time. Why is this happening and is there a waythat I can keep it from happening? What can I do to avoid this inthe future?
Thanks for the help.SolidworksAssemblies