Vista - Internet Explorer 7 (with tabs!)

So here is your question:

You can drag a link from one IE window to another and the page will open up
in the window where you dragged the link to.
Works that way with pretty much all web browsers.

How do you drag a link from one IE tab window to another tab window within
the same IE instance, without opening a new instance of IE?
If you click on "Open in new tab", it won't use an existing tab, it will
create a new tab.
I want to drag into an existing open tab. Ideas?

-- Andy