Is it possible to backport the breadcrumb style address bar from explorer in the 3683/3718 builds etc into Windows XP SP3, and if so, pleas ecould someone tell me how it is done? Thankyou!

Short answer.. No.

Longer answer... Not directly, as it's built into Explorer itself, however, you could try writing a toolbar to repliate it, if you can manage to tap into the API to grab the current location of the Explorer window.

have a look at the application "QTadressbar", it is exactly the vista bar..

requires .NET 2.0 on XP.