assemblies opening in same window........

for some reason when i try to open two different assembliesfrom two totally seperate folders if two parts within theassemblies are named the same they try to open in the same window.if they are from different folders why is this happening?
a lot of my ass. have the same part names.we do handrails etc so wehave parts like glass, posts,handrail etc.
any ideas?SolidworksGeneral