DuoExplorer is a free and portable multi window file explorer or a "Dual Window File Explorer". It can be used to navigate two directory structures from a single split view file explorer window.
SE-Explorer is an awesome Free Portable File Manager and Explorer for Windows (Windows File Explorer Replacement). SE-Explorer features a tabbed interface with dual pane browsing, a file search option, a file size scanner to help locate the largest files, resource (hex) view for exe files and icons, syntax highlighted text viewer, built in web browser and much more.
Explorer++ is a Free Portable Explorer that can be installed to an run directly from a USB device. The Windows Explorer clone features many additional enhancements such as multi tabbed browsing, thumb preview of images as they are selected, drag and drop support, file merging or splitting and more.
Free Commander is a Free Portable File Manager for USB. Proclaimed as an excellent alternative to the windows file manager, it is easy to use and get accustomed to.