Not sure why you'd want to do this, but someone has created a case-sensitive version of Google search at http://case-sensitive-search.appspot.com/. While I can see some possible uses for this, the site works by getting all the search results and culling out the ones that don't match the entered case sensitivity. Not exactly the most efficient method. But I guess if your stuck for case-sensitive Google search results, it'll do in a pinch.