Although the operating system provides its own file management system, you can buy separate file management systems. These systems interact smoothly with the operating system but provide more features, such as improved backup procedures and stricter file protection.

Hard Disk Logical Structures and File Systems 
Describes "standard" file systems used on PCs, with particular focus on the FAT file system and its variants. This page is from "The PC Guide."

Yahoo!'s file management software and utilities page
Yahoo!'s directory of file management software and utilities.

Understanding File System Options
Whether you're looking for a refresher on files systems or want to learn the difference between FAT file systems vs. NTFS file systems, this tutorial explains the ins and outs, and pros and cons of each.