Folder Axe is a free software for Windows that helps you split large folders that contain a huge number of files into several smaller ones, while keeping all your files in order.
You can split the main folder according to the number of files you want each new folder to have, their size (as a maximum number of kilobytes, megabytes, or gigabytes), or by name (each new folder will store the files that have a name starting with the letter that you specify).
The whole process is fast and straightforward. The new folders will appear inside the original directory, and all the files will take their new locations automatically.
Folder Axe is a great tool for reorganizing and classifying your cluttered folders, without taking too much trouble in the process.