使用Interop.SHDocVw.dll我在哪里可以找到这个命名空间/ dll？

I've done this before, I don't remember if i downloaded the DLL from off the net or something but i don't want to get a virus. I need access to this namespace so that I can have extra features that the Webbrowswer control doesn't offer. I've done this before, I don't remember if i do