ASP.NET DLL

Question

I have an asp.net project i which i am already using a one DLL with name "DropDownCheckBoxes" now i also need an implementation of another task and from internet i get another DLL which works fine for me but when i add the new one which has the same name the previous gone , how can i add these two DLL both having same name or what can i do to use the functionality of both ??? ASP.NET question that is ??