FileCommander

FileCommander is a small-sized and portable file manager that provides a handy set of tools for performing file operations, including multi-screen viewing mode.
Since installation is not a prerequisite, you can drop the program files somewhere on the hard disk and run the executable directly.
It is also possible to save FileCommander to a USB flash disk or similar storage unit, in order to run it on any machine without prior installers.
What's important is that the Windows registry does not get updated with new entries, and no additional files are created on the HDD, leaving it clean after product removal.
The main application window contains four tree views by default, and you can switch to one, two, or three panes.
Its context menu contains similar options to Windows Explorer, along with new ones. For example, you can swap or match windows.
It is possible to copy or move files to other locations, create MD5 signatures, select files by extensions, quickly compare two windows, view console details, change the visual theme, as well as show a file preview window.
Other options of FileCommander enable you to edit a list of tools to be used for web browsing, editing pictures and text, and others. By default, FileCommander detects the programs installed on your computer and automatically sets them as default.
From the "Extras" menu you can view currently active processes, installed software and drivers, open a DOS command window, split or synchronize files, use a search function with file masks, as well as add or remove virtual hard drives.
As far as program configuration is concerned, you can enable FileCommander to autorun at system startup, integrate it into the Explorer context menu, set it to minimize to tray, select another GUI language, enable gimmicks (e.g. local weather), as well as set up the file copying behavior (e.g. apply source file attributes to target, set operation on "drag and drop").
FileCommander uses low CPU and RAM, has a fair response time and is compliant with newer operating systems, although it has not been updated for a long time. There are some stability issues, though, such as performing drag-and-drop operations.
Unfortunately, FileCommander has been in beta development stage for a very long time, and it doesn't look like the project will be finished anytime soon.