I recently found on http://on10.net the wunderful and "Must-Have" tool QTTabBar.
The QTTabBar is a simple but powerful AddOn which gives you seamless integration of tabbed browsing of folders and directories right out of your standard Windows Explorer.
It works on Windows XP (with installed .NET framework 2.0 ) and Windows Vista.
And the best: it is absolutly free! Go and get it...