I could never figure out why Microsoft never offered a dual paned or tabbed view interface option in Windows Explorer. Managing your files and folders in those types of interfaces are so much easier to use; especially if you are a power user.
There are numerous third party options available; however, none really mimic the Windows Explorer interface, until Windows Double Explorer came on the scene. Windows Double Explorer is an open source utilitly that is engineered (for Windows 7) to manage two or more Windows Explorer interfaces in one application.
Windows Double Explorer also features a vertical or horizontal dual pane interface in conjunction with a tabbed interface. Once you have Windows Double Explorer up and running; and configured to your liking, I think you will become hooked.
Windows Double Explorer is currently in the beta stage of development and is engineered to work as a Windows 7 application. There is no install to this application. Simply download and run with it.