There is a lot of free alternatives to the default Windows Explorer. Just to clarify Windows Explorer is what you see while you are browsing files, Internet Explorer gets you to the Internet. One of the alternatives is Cubic Explorer. CubicExplorer looks rather similar to Windows Explorer except it adds a few neat features like: tabbed browsing, more viewing options and more quick navigation buttons.
The next alternative browser is Explorer++, this browser also adds tabbed browsing as well as more viewing options. It is different by: adding easy-to-remember keyboard shortcuts, customizable user interface, drag-and-drop support even with Windows Explorer, many advanced features including file merging and splitting, and this application is completely portable.
Xplorer2 is an alternative that has a lite(free) version and a Professional Edition that costs $29.95. The lite version comes with explorer functionality, tabbed browsing, and an optional Internet search bar. The Full version has everything in the lite version and metadata viewing, search text inside of office, PDF, and other file types, compare and sync files, discover and clean up duplicate files. This browser also allows you to customize the look and feel.
These are just a few of the examples that are out there. It is really up to you to choose the correct one for you and meets any needs that you have. Just go out and try a few, there is a good chance that you will never return to the normal old Windows Explorer.